WARNING: Generalisation based off my personal experiences

In high school: I had an extremely gorgeous friend in high school. I was friends with the guys and they all had secret crushes on her but were too scared to approach her. But when people complimented her or mentioned how good looking she was, she was incredibly humble about it and said that her looks didn’t make her feel confident. She didn't have an ostentatious social media presence, which baffled me because if I had her face, I would’ve been all over social media with it. But it was always the average to slightly below average girls who kept plastering their selfies on Instagram or Facebook or whatever. The good looking ones kept themselves low-key (a few of them waited until after high school to start a social media presence) And it was always the average to slightly below average girls getting boyfriends (who all had a secret crush on my friend) because I suppose those girls seemed more attainable to them. My friend wasn’t popular and didn’t have a lot of friends, but a lot of people (both guys and girls) would gush about how good looking she was behind her back. The “popular” girls hated her though, probably because they would never be as good looking as her despite their popularity.

After high school: I have dated around, both attractive and (conventionally) unattractive guys. What confuses me is when an incredibly attractive guy opens up to me about his insecurities and how he wants to improve his appearance... like what?! You look like you could be a model or movie star! Why the low self esteem??? And these attractive guys are less superficial about their choice in women than the unattractive guys. They would tell me that they like women of all sizes, women in all sizes can be beautiful and a good heart is what matters. But the unattractive (or conventionally unattractive) guys I have dated have ALL been so confident and comfortable about themselves and how they look, to the point of arrogance. They would even confess that they are happy with how they look. They would tell me that they could never date an ugly or fat woman and have confessed that they are incredibly superficial about appearances. These men would warn me that becoming fat and unattractive is a dealbreaker. But like bro... have you seen yourself?! I mean it would make sense if the attractive guys I date had this attitude because they are attractive and probably want someone equal to their attractiveness, but it’s never them - it’s always the less attractive guys with this attitude. The attractive men doubt their attractiveness.

Besides being based on my anecdotal experiences, is there a science behind this?

Also apologises if this is in the wrong forum! I wasn’t sure as to which sub to post this.