Ask HN: Is Mentorship a Thing?

In recent years, I see a lot of advice related to mentorship, typically on Linkedin "Seek Mentors or Coaches".

It seems everyone and their mother has a mentor or is trying to find one, but I've never seen any such mentoring occurring in my circles (I don't count official mentoring, such as intern supervision). Also what would be the benefit for the mentor? let say someone is very senior in their field, are they expected to use their free time to help someone without anything in return or is that a paid service?

Curious about your experience.