I already wrote about this in the thread linked by /u/Holy_Shit_Heckhounds, but it's always worth expanding on just how unhistorical and even anti-historical the tech tree model is.

While tech trees work fine for a game, their fundamental flaw is that they treat technology as a quantifiable substance - something you can produce, collect, and own. Something of which you can have more than other people, which gives you an advantage even when you are equal in all other respects. From a historical perspective, this is simply not what technology is. There is no technology mine from which you can dig up more technology to put in your technology storehouse.

To put it simply, technology is practice. It does not emerge or exist outside of its practical application within a society, economy, or culture. It is not pursued or preserved for its own sake. It has no intrinsic value. A given technology either has a use (in which case it may be developed and passed on) or it doesn't.

Writing is a good example. The Mycenaean Greeks of the Late Bronze Age had a syllabic writing system (Linear B), which we can read. They seem to have used it primarily to keep administrative records: palace inventories, letters between governing officials, and so on. But when the palaces burned and the administrative structures that ruled from them disappeared, writing went with them.

When writing re-emerges in the Greek world some 400 years later, it is completely different: an alphabetic system, directly based on the Phoenician alphabet, which seems to be primarily used to mark objects with names and lines of poetry. The first written works of Greek literature are all poetry; it takes a century for the first written laws to appear, and many more centuries for writing to be reapplied to practical administration.

What happened here is not that writing was "lost" in the sense that people forgot how it worked and couldn't make it work anymore. Rather, with the fall of the palaces, writing simply lost its practical application. Why would anyone pass on the art when no one was using it for anything? Why would anyone take the time to learn how to write when there was no status or advantage to be gained that way? Writing didn't come back until a much changed society found a new use for it. (We could argue that the alphabetic script was objectively superior to the old syllabic one, but this is irrelevant because the Greeks had long forgotten it.) Again, technology has no value of its own; without practice, it is worthless. That includes technology of which we now think the value is self-evident.

You are right, then, to assume technology shouldn't be seen as a linear process of compounding improvement. But it also shouldn't be seen as something you need to "maintain" through the investment of resources. Rather, certain technologies will be kept when your society is currently using them, or lost when it isn't. This is in fact the same process as what we call "progress". Probably the most common reason for technology to be lost is the introduction of new technology that does the same job in a way that a society or culture perceives as better or more suited to its needs (cheaper, faster, using different materials, better aligned with other cultural practices, etc etc).

When modern states "invest in technology", they are still not pushing the creation of new tech for its own sake. They are creating and fostering a culture in which the invention of new technology is associated with wealth and social status. That is its practice. When we perceive history as a linear progression from simple to advanced technology, it is because we are so captured by a culture that values technological progress as a moral and social good (creating a practical use for technology even when the technology itself is useless) that we lose sight of how artificial this perspective is and how technology actually works historically.

More can be said, but this might interest you: Someone on an Ask Reddit thread claimed research indicates that prior to Ptolemy VIII exiling academics from the Library of Alexandra, "they were only about ~300 years from full on industrialization." Is this true? If so, where can I learn more about it? written by u/Iphikrates and u/rememberthatyoudie

This is more of a clarifying question than a proper response but I have a few examples up my sleeve too.

It's not like 6th century Italians looked around at Roman aquaducts and wondered "what the heck are those things?" They knew what they were and retained the basic principles of their construction. They built enclosed irrigation systems, after all, and bridges. Combining those two technologies gets you aquaducts but it's expensive and difficult and not the sort of thing that anyone without a population center the size of late Republican Rome is going to bother with.

So, I think we need to separate the concept of "did people forget that something was possible" from "did they lose the ability to do it" from "did they just stop doing it because it wasn't worth it anymore."

Continuing with the Roman period, the Augustin legions used a banded mail breast plate called the Lorica Segmentata. The use of that armor diminished as the empire declined due mostly to expence and diminished need but it's not as if Romans couldn't make one if they felt like it.

Contrast that with the construction of the Pantheon dome - a free standing concrete dome, the likes of which wouldn't be seen in Europe for about another 1000 years. Generations of people walked through the Pantheon who had absolutely no idea how one might build such a thing. But they still knew that domes were possible... just beyond them.

I'm struggling to come up with an example of an actual lost technology - one where even the idea of the thing vanishes. The best I can manage is the use of primitive steam engines in children's toys and the like, but I expect that's a failing on my part rather than historical contemporaries. I expect that someone with a better background on the history of steam power could document continuous knowledge that boiling water can turn thermal energy into rotational energy.

But - back to that clarifying question. When you talk about a technology being lost, which of these do you mean?

Historian of technology here. The way you describe technology as something linear and progressive, and how these games portray it, has long been a very dominant way of thinking about technology. It's essentially thinking of technology as a series of groundbreaking innovations. And when a new innovation comes, it replaces an old one. Still a lot of people, and especially also politicians, think like this.

However, historians of technology have disproved that view for a while now. Historically, technology has not developed linear, and if you stare blindly on innovations and new technologies, you will miss out on a lot of aspects of technology. Most of the technological development is about slow incremental improvement and maintenance.

I will give you an example: if we think about coal and steam engines, what is the century you would associate that the most with? Chances are that you would say the 19th century. Well, there has never been as much coal combustion as at the end of the 20th century. Fossil fuel power plants have never been as efficient as now, due to constant improvement and maintenance. We don't only have to look at when something was invented, but also when it is used.

Another example from my own research: when you think about nuclear power plants, chances are that you immediately think about uranium, futuristic control rooms, white lab coats, and radiation. Well, 80% of most nuclear power plants are water or steam components: pressure vessels, steam generatores, valves, pipes, pumps, etc. The first nuclear power plants were essentially spin-offs of fossil fuel power plants and nuclear weapons labs. And nowadays, more money (and political effort) goes into maintaining these old installations than in designing new ones.

So to answer your question: maintenance has only recently entered our thinking about technology, and this insight is still very absent in society I feel. And that's a problem I think, because if we were, we would devote much more resources to actually maintaining our current infrastructures (for instance, crumbling highway bridges, train tracks, corroding power plants) instead of only on innovation. And these games are not helping by spreading an essentially outdated view on technology.

In case you are interested: a great reading tip on this is Shock of the Old by David Edgerton.