> If they're not just homebody introverts in the first place, they may already have a pretty saturated schedule/network without many suitable people around to pair off with.

Then they really don't have the time for a relationship. Maybe they just want a hook-up, but that also takes time to connect with people and build relationships for something casual. It's all just work, at the end of the day, and a lot of people are unsatisfied with that answer. Things like being on the high-end of attractiveness are like cheat codes, but those people still have to put in effort to connect with people before they get to the fun part.