My boyfriend has no close friends.... should I be concerned?

My amazing, caring, kind, understanding boyfriend of 1.5 years had 0 close friends. We are both in college and its my hometown but he moved from the city he grew up in about 8 hours away to come to college here. I’ve only known him from college but from my understanding he had close friends back home that he lost contact with once he moved here (he is now a senior and has been living here for 4 years.) He is a bit on the shy side but has no problem interacting with people but just doesn’t have any close friends. I have a lot of very close friends and I feel like I’d be lost without them and I know not everyone operates the same way but sometimes especially when we fight I kind of worry about his well being and wish he had someone to rant to about me. He had one close friend that recently graduated and moved away so after that he doesn’t talk to anybody except me. He’s been very stressed about school lately and I’m just worried about him. He is truly my best friend and I think I’m his but am I wrong for thinking he should have more friends? He tries to be social and attend campus social events but most of the time if I don’t want to go he won’t end up going because he doesn’t have anybody to go with. Any advice?