You are right, of course. But just think if the CAFE were relaxed a bit. My 435hp Mustang might get 500...
But the optimization is mostly accomplished by computer controls. I hate that I’m driving a server, and if some little sensor malfunctions, it could literally shut off my engine for no reason... AND it will COST me to get it fixed, when the car would run just fine without it. (When my backup camera goes out, I just turn and look behind me - remember that?)
I would rather replace a crankshaft position sensor by the side of the road than tear a carb apart that is badly leaking hot gas onto the engine.