Sitting backwards is beneficial if looking at accidents.

But sitting backwards is very very uncomfortable if there is any kind of uneven acceleration, bumps, swaying, rolling, curvy tracks or whatever. Humans need to look forward at the horizon to get their visual stimuli aligned with their motion/balance sense in the inner ear. If that alignment isn't there, you will get seasick. Backwards makes this even worse.

Babies don't suffer from this, because closing your eyes helps, and infants don't have as strong a reaction to motions anyways, due to them usually being carried by their parents until walking age. So reverse baby seats only work for babies.