It's a chicken and egg problem. No serious gamedev company is going to invest in code that is capable of taking advantage of new stuff when there is not a single one device on the market (and the issues of the first generation known and work-aroundable), and no chipmaker is going to invest into radical modernizations if there is no demand.

And you get that code by giving developers hardware to run it on. Outside of some hardcore early bring-up guys just about no one develops software on models and emulators.