I record for a few reasons:

1. Just in case something happens I may have a record of it
2. To learn from my mistakes

I have a 40-50 min ride each way and there are times where I recall doing something wrong but don't have the time to analyze it on the bike. Being able to watch it later helps me do that.

The reason I think less people in cars do this is because the buffer between accident and death is very high in a car so there's little value in recording the event. However on a bike, that buffer is almost nil in many situations.

To support this, consider how many people in Russia have dash cams. They don't do it to learn from their mistakes, they do it to protect themselves from insurance fraud scams and general crime because it's such a significant problem there. Their buffer between themselves and something terrible happening to them while they are driving is similar to the buffer that cyclists often times feel exists between us and the other drivers on the road.