I spent almost all of my junior and senior high years being a loner. It wasn't until a decade after graduating that I tried to expand my social group and try to fit in with others, mostly classmates as you described. I think most people are good at heart, but they are still likely to join in the mob riots. They are good in person and one-on-one, but vastly different when they start kowtowing to the social rules of their clique. I tried to have patience with them, but it ended up being a losing battle. It takes quite a lot of effort to keep up with them, and the benefits really aren't all that worth it.
I'm going to side with the idea that they may actually mean good by trying to invite you to things in person, but that's only short term gains. If you're lonely, it might be nice to have a night out with some classmates, but they probably aren't going to become best friends.
Unfortunately, I've started becoming jaded with the idea of hanging out with people just for short-term gains. I feel like I'm using them, and maybe that's just me over-thinking it, but that's how it feels now. I'm not sure where the line gets drawn there, so it's easier for me to just steer clear of that kind of social interaction altogether. I don't like it, though. I'd like to be able to have more casual friends here and there.