I think there are several reasons not to do it: People get sick more often if riding against moving direction (back).There are more rear end hits than full frontal hits. In the front-lateral hits or side hits, passenger attention helps countering the crash effects.

Undoubtedly this would increase safety in passenger cars, buses and airlines, but there is a common prejudice which I share in which I prefer to see where I am going.

I'm neutral on the idea, but the idea reminds me of a story. When I was in the Air Force, I took a cargo flight with several seats facing backwards. One passenger, an experienced F-16 pilot, sat backwards. Although he could handle high G-forces, he couldn't sit backwards. He vomited his lunch.

Besides the obvious problems, how could a passenger help with directions?

Clearly not posted by someone who suffers from travel sickness. Even the idea makes me feel a bit queasy.