I don't like what I'm going to say, but post scarcity can't come without either a worldwide culture change or an exploding population that would lead back to scarcity.

We are still animals, and evolution is still a thing. We're clearly a k-selected species, but in post scarcity, what's to stop a portion of us from becoming r-selected?

https://en.wikipedia.org/wiki/R/K_selection_theory