Tell that to our artists 😉. As a coder I'm all for procedurally generated content. I did replace several heavy textures in our games by procedural materials, to squeeze out a couple of extra MB. However, that's not the way artists traditionally work. They often don't have the programming knowledge needed to develop procedural materials on their own, and would need to rely on technical artists or programmers to do so. Drawing a texture however, is very much part of their skillset...

But yeah, the mention of "squeezing out a couple of MB" brings me to another topic, namely that (at least in our games) the on-disk textures are only part of the RAM usage, and a relativley small one on comparison. In the games I worked on, meshes made up a significantly larger amount of RAM usage. We have several unique assets, which need to fulfill a certain quality standard due to licensing terms, such that in the end we had several dozens of meshes, each over 100 MB, that the player can freely place... Of course there would still be optimization potential on those assets, but as always, there's a point where further optimization hits diminishing returns... In the end we had to resort to brute-force solutions, like unloading high quality LODs for meshes even if they are relatively close to the player... Not the most beautiful solution, but luckily not often needed during normal gameplay (that is: if the player doesn't intentioally try to make the game go out-of-memory).

But I'm rambling. The tl;dr is: The memory constraints would not be a big deal if there was enough time/money for optimization. If there is one thing that's never enough in game dev, it's time/money.