I think for a lot of young people particularly it's both; the desire to conform, but also the desire to stand out and be different. Social media has a lot to answer for on both those counts.
I see it in a young family member (in her 20s). She's desperate to be seen as a sexy TikTok girl (so loads of pouty filtered selfies, miming along to songs in a what she thinks is sexy fashion etc), and at the same time over the last year or two has diagnosed herself with autism, ADHD, bulimia, dyslexia, dyspraxia, anxiety and depression. She may well have traits of one or more of those things, but has no diagnosis, not even seen a doctor or other professional about any of it. But posts and shares memes about having one of more of those things, a lot.
Or maybe that is also a desire to conform if other people in her social circle are doing it too, who knows. Regardless, she gets attention, it makes her feel good, feel noticed, feel special.
I think SM for older people who didn't grow up with it is in a way less harmful; for most of us our identities are fully formed, we don't need validation from strangers and we use it as a tool to keep in touch with friends and look at pictures of puppies, find recipes or whatever. That's certainly how I use it.
It seems to be so different for a lot of younger people, it's intrinsically part of who they are and how they present themselves to the world, and it sets an entirely different set of 'norms' that then follow through into the real world.