By that logic, we should eliminate paternity and maternity leave, because why should people without children work to fill in the gaps left by parents?

Isn't that kind of how society works? i.e. If a senior employee benefitted from having close mentorship and a strong social network when they were a junior, then they may wish to pay it forward by being present and mentoring juniors now that they're a senior.

Yeah probably, the outlook for their kids ain't looking so great.

Yes.