I didn’t think people who stay in stable long term relationships look at it that way. The first thing to realize is that our brains are wonderful things. For instance I know my wife isn’t going to model on the front page of Sports Illustrated any time soon. But to me she really is more attractive.
The more we find out about how our brains work in relationships, the less the idea of having to be perfect makes sense. Both with beauty and personality. If you have the best body and personality according to society then you’re not unique. Millions of people are trying to make themselves into that image. Being yourself and being healthy are far more likely to land someone who actually cares about you.
Being attractive is mainly helpful in getting dates and having casual sex. Beyond that there needs to be actual compatibility of some kind, solid relationship skills, and a willingness to work at the relationship. Those are far more important over the long term than classic beauty because when you’re older that’s what’s going to be there.
That all said, I’m not aware of anyone “settling” in the modern era. We seem to be far more content with our friend groups unless there’s really something there.