A modern history book is mainly just blocks of text, something which hasn't changed despite the access to computers everywhere.
The answer is probably an obvious one, that historians can't make use of the new media but I am wondering whether that is intentional. It shouldn't be a problem at all for a history department to collaborate with the computer science department.
As an example I could refer to science textbooks. They would often include CDs or links to their website where a student can access software which illustrates the subject better than a still image ever could. A medical student has access to webbrowser application which lets him surf through the body naming and describing every little anatomical feature. And a physics student can plug in numbers into a simulator and get his results in real time.
When I read a history textbook, the references are marked with a small number and I have to go to the end of the chapter to see what it refers to. If I am lucky, there is a small description of that reference. That could be made a hyperlink in today's media. I should be able to hover over any reference in the text and get a small portrait of that reference. Further, it should be possible to have high resolution images. So much detail is lost when an image is fitted to the page of a book.
And when we are talking about the study of material culture. Why wouldn't I be able to get a high resolution 3d image which rotates before my eyes? That by the way can be achieved by anyone at home with the very simple use of software. All it takes is 50 photos of that object. With the 3d image comes the availability of data. Material, dimensions, weight, gps coordinates of where it's found. That kind of data should be a simple click away from the text.
Or the use of maps as in this news article which recently garnered a lot of praise on reddit: A Game of Shark and Mirrow. The New York Times had the resources to put that much work into a single article.
As an example I could refer to science textbooks. They would often include CDs or links to their website where a student can access software which illustrates the subject better than a still image ever could. A medical student has access to webbrowser application which lets him surf through the body naming and describing every little anatomical feature. And a physics student can plug in numbers into a simulator and get his results in real time.
When I read a history textbook, the references are marked with a small number and I have to go to the end of the chapter to see what it refers to. If I am lucky, there is a small description of that reference. That. could be made a hyperlink in today's media. I should be able to hover over any reference in the text and get a small portrait of that reference. Further, it should be possible to have high resolution images. So much detail is lost when an image is fitted to the page of a book
...these kinds of history textbooks do exist, you've probably just had teachers who are sticking to older editions. For example, the most recent editions (3d or 4th?) of Barbara Rosenwein's A Short History of the Middle Ages have an online site that features study questions, genealogies and images while Eric Foner's Give Me Liberty has way better online resources that include: "exercises, interactive learning tools, assessment, and review materials, including: quizzes, flashcards, and video exercises."
You're being selective in your examples. There are science textbooks which are mostly just blocks of text, and there are history textbooks which are as you describe they should be.
Heck, just today I attended a presention of a history 'textbook' which doesn't even include a book anymore. It has everything you describe*, not even "a simple click away": hovering your cursor is enough. It's awesome stuff and it shows you're being prejudiced when you say that "historians can't make use of the new media" (what kind of bullshit is that?)
*It doesn't have custom-made 3D-models; that's not as cheap and simple as you make it out to be.
There has been a lot of digitalization happening in historiography the last few years. I've even done research with sources fully available online. You often need a University connection to access those, but still.