Indeed, great points to add, thank you for the feedback.
There is usually always a reason for us to do something, so indeed if sharing wasn't to establish credibility, trust, loyalty with others, to gain credits for future help we may need in the future, or to simply be happy doing it, then we wouldn't do it like you say. The intent to appear better or get noticed for being "nice" also plays into that social reciprocity of our lives, cred for future help requested. "Look at that guy helping, he's so great, I'd help him out next time he needs help because he's helping others."
Thanks again for the good points to add.