Even if this wasn't asked statistically more then when doomstacks will be gone, it still is a sensible request, is it not?
Back to topic: I think the reason there is no ingame tech tree is, that it's not much of a tree, but rather a big stack of random techcards, with a few that require other techs first. These requirements, as well as an overview of what techs could be achieved, would be nice to have access to ingame without external sources, since you actually need specific techs for certain ascension perks. So it would be reasonable wanting to know how to get these techs in the first place.