To increase the odds of being thanked, some people compliment some people; some make kids.

Grandchildren are their grandparents' toys.

As a subconscious attempt to add meaning or purpose to their life: The unemployed pray for a job; the retired pray for grandchildren.

Most parents are not really ‘supportive’ because they want their kid(s) to succeed; they ‘support’ their kid(s) as an attempt to avoid appearing to have bred a failure, or, failures … in the eyes of their peers and/or neighbours.

Being a 'good' parent is more about the parent, and, less about the 'supposedly-could-have-been-bad' child.