I think if most people are honest with themselves, a lot of behaviour is all about image and looking good.
I would say that it is related to ego, and not having a well-developed 'healthy' ego means it is likely that peeps will seek external validation for themselves.
I like to look good, I find it really empowering, but it is not the most important thing.
I am not sure how old you are, you are quite astute.
All I can tell you is what my mom told me, life gets better as you get older.
I have been finding this to be true, I think my teens were the WORST time in my life, really YUCK, and probably due to some of the things you were talking about.
I have been a sciencey book geek (yet 'jock') most of my life, I didn't do all the girlie make-up etc stuff until I moved to Europe. My looking good used to be looking BAD