Artists usually show their pieces to at least some other people, yet many paint for internal contentment - we are fundamentally a social species. A large part of experiencing something is showing it to other people to seek their opinion/approval - especially if it had a large impact on a person. More to the point, beyond simply surviving, why do anything? What is life's goal? I would put it to you that many people like this were raised in such a way that their internal contentment and pride comes from this kind of thing: they judge people and more importantly themselves on the experiences they have had and the joy they get from it. They feel a need to share to get some of this joy - usually with loved ones and friends, but sometimes wider.

This is not a bad thing: People often also have a need to hear about others' experiences - hence books, videos, and you being here on hacker news.