Interestingly, I think people like you and me use Lemmy because one of the same underlying reasons as social media people:
Either:
Endless amounts of stuff that speaks to your interest. (With us it's stuff like technology. On Social media, people are "interested" in what others are up to.
Getting likes/dislikes. Even though likes aren't important on Lemmy, I notice in my usage that I do subconsciously get the same dopamine hits jf a post gets liked a lot, just like Social Media does. It's less aggressive on Lemmy because you don't get alerts for it, but it does factor in on engagement.
Engaging in conversations/discussions with other people.
Sharing things you find interesting yourself
The content might be different, but the underlying principles are really close. Social Media is actually really close to how forums work at it's core.
But I know this is an unpopular opinion. And no, I wouldn't call Lemmy Social Media per se. But the line is more blurry than I'd like to admit if I look at my time spent with Lemmy.