I think with how unergonomic airplane seats have gotten, there's a real health benefit to minimizing the time people are crammed in those cramped seats.

If they made airline seats reasonably sized and ergonomic, sure, the flight time matters less, but right now the longer the flight portion is, the longer my back will complain afterwards. I'm not even unusually tall or heavy-set.

Airlines won't make the seats bigger since that would cut into margins, but if the planes are faster, they can run more flights and pay the pilots/flight-attendants for fewer hours, so that feels like it's a solution that's more likely to happen than the real solution, of making it so the seats aren't designed to destroy your back until you pony up for business/first class.