I think it is a combination of things, people feel insecure or are under pressure to look / dress in a certain way.
I have seen reports that girls who feel bad (or just insecure) about how they look. Maybe on example you feel you are over weight, the algorithm sends you pics of thinner people.
It just adds to more stress on something you may not have control over.
That coupled with people being nasty, using social media to bully and be nasty to others. But that is a social issue, i think social media gives people that platform to be nasty via a platform rather than to someone's face.
There is some sort of belief you need to look a certain way to be successful, people judge you, a lot of pressure on younger teens whos bodies are still developing.
@alienghic Another reason I want toget people on here with some expertise in this area, not just here but on the activitypub forum so we can make fedi better based on real evidence.