Frankly, I find it annoying and also a bit sad. Most of the posts that get a lot of attention have these really long and pompous titles. Ideally, explanations and elaborations should not be in the title but in the actual post.
Also, most of the information provided in the long titles is often only fluff, entirely superfluous. A recent example: "Why has the location of the river Rubicon been lost?" would've entirely sufficed. Anyone who could even attempt to answer this question obviously knows what the Rubicon is.
(the title I've chosen here is of course meant as a joke)
A brief bit of context in the title helps establish why you're asking the question, and that context can be important in catching people's eyes. Sure, a question can be boiled down to a single sentence for the title with all the other context placed in the post, but sometimes that prefatory line in the title makes a difference in whether or not your question gets noticed, and in turn, upvoted and/or answered. Knowing why someone is interested in something helps you give a better answer, and if the context is solely found in the post, then someone who could be able to answer it might not always see it and know they can contribute.
An example: a few months ago, someone asked In the novel 1984, the Oceanian regime enforced “Newspeak” in order to limit a person’s ability to think and articulate “subversive” concepts. Were there any actual totalitarian regimes that attempted to exert the same or similar control over language? This question could easily be retitled to something along the lines of "Have authorities ever used language to manipulate thought?" with the context drawing a connection to Orwell. This question got a few good answers that this alternate title still could've produced. But by drawing a connection to this very popular novel upfront, it caught more people's attention, leading to more upvotes, meaning more people were able to add to the discussion.
But more importantly (in my mind, anyway), by explicitly referencing Newspeak at the beginning, it drew a connection to my particular sub-field. While I can write a little bit about the intersection of authority and language, I wouldn't be able to put together a satisfactory answer to the exact question. If a thread with my proposed alternate title was posted, I'd have nothing to say. Buuuut since Newspeak is an important item in my field, I was able to look at the question from a different angle: instead of talking about language policies similar to Newspeak, talk about what influenced Orwell to put it in 1984. This gives me a way to discuss real-life similarities to Newspeak without actually talking about policies that places have implemented—an interesting thread that is adjacent but still close to what OP and other readers are looking to learn about. (Plus, focusing on how Newspeak worked in the book might have helped produce another, far better answer from someone else later on in the thread.)
Some forms of browsing reddit allow you to see some of the post content while scrolling through your feed, but not everyone uses those forms, or has that setting turned on. Putting something in the title really does help people know what you're asking about, which can produce better results.
(Also, they help make questions more fun. Sure, I could just ask about how kings were expected to engage with science, but leading with a famous Monty Python quote not only explains where I'm coming from, it also [hopefully] puts a smile on people's faces when they see it.)
I don't have a definitive answer, even if it is enough of a phenomenon that I easily know what you mean, but I am interested in your impression "This is a trend I've not seen elsewhere on Reddit." If anything, my impression, and assumption on 'why', has always been that it is a very 'reddity' thing to include superfluous information in the title. And in the context of this sub, in particular, by assumption is that users think that an interesting title, which goes beyond that specific question itself and offers some context, makes it get more attention. That might actually be correct, even, as there is a specific subset there which when I see it get posted, I feel like I have a pretty good success rate on the thought of "Yeah, that is going to hit the top!". But we've never done anything to look into whether it improved the chance of an answer, beyond the broader correlation of upvotes.