Trading social media/numbers but no chat?

I find it so odd when I someone asks for my socials or number, but then they don't chat or respond well. Why ask for someones details and then not hold a proper conversation? It happens literally every class too whats with this trend? I'd assume that trading socials would mean you'd want to get to know eachother better or at least be familiar enough to be study buddies but I guess thats an unpopular opinion lol.