Everybody is different, man. I have extremely deep insecurities with sex, so any part of this would be painful. Because of some childhood events, I have a hard time feeling comfortable sexually around anyone except women, and even then it takes time.

But recently I was hanging out with some acquaintance/friends for a long time(like 5 months in the same room straight) and they broke it down to me in a way that makes much more sense.

Some people like the feeling and idea of sharing pleasure with their peers. It's a feeling of unity and community, like hey, this feels good, I want you to feel good, too. This is perfectly natural and healthy with all consent. This is prosocial behavior.