Something I notice is that people who were attractive when I was in middle school with them are still like that almost a couple decades later. I figure it makes sense though if you look at taking care of oneself as a skill→[More:]

Same as if someone was good at math or spelling when they were 12, they won't necessarily stop being good at these things unless they stop practicing them. So if someone took care to fix their hair in the mirror, dress well and not eat junk food when they were adolescents they're not gonna stop doing these things (unless they change habits for whatever reason).

Personally I do remote work a lot and it's super easy for me to go days without shaving my beard or caring what I'm wearing etc. I realized a long time ago though that if I suddenly need to get "ready" to go to an event it's hard to go from 0-100 (ie. from 'letting yourself go' to 'looking your best') in one day. It's a subtle thing and I don't have any objective data points but I find when I start caring about my appearance it takes weeks before I get to the 'Next level' where my skin looks better, I've chosen the right clothes, (and this is not counting things like fitness where it might take months or years to turn things around), basically it takes a few weeks of "getting it together" before things "snap into place."

So, I don't necessarily have a concluding point. I guess the common thing between these two observations is: while there is no doubt that some people are blessed with advantages in looking good (good genes and other things they were born with, time and money to take care of themselves, good health and all the rest of that), a major aspect of it is tending to oneself as a skill; as with any other pursuit it takes time, experimentation, ongoing practice...