I disagree on your point that resources will remain scarce. That's true of earth, but long-term, which is really what I'm getting at, that's not the case. We aren't even that far off from mining nearby asteroids; give humanity 100 years, and who knows what we'll be up to.

UBI is a stopgap in that it just extends the current system by giving away money; eventually we'll need to move past 'money' somehow.