What would regulations look like that took market reality into account? The whole point of regulations is to go against what the market will buy without them.

What would regulations look like that took market reality into account? The whole point of regulations is to go against what the market will buy without them. If people bought low emission cars without any outside forces then you wouldn’t need any regulations. Of course, in reality that path leads you to smog-choked cities and lots of dead people.