It is easy to make something like that. It is less than easy to interface something like that with a full game engine. Things like requiring collision culling

It is easy to make something like that. It is less than easy to interface something like that with a full game engine. Things like requiring collision culling (not doing the whole O(n^2) "check if A is colliding with B" thing), doing proper shadows, being properly deterministic, being alright with variable framerates, that sort of thing. Also, I don't know what simulators you've seen, but the ones I've seen take an absurd amount of CPU time. Or occasionally GPU time. Works well for a proof-of-concept. But for a full game... Their priorities are elsewhere. Not worth the cycles. That being said, I fully agree that game focus should be shifted slightly away from straight graphics and more into gameplay.