Why is this guy always alone?

There's this guy at work who's in his 30s and literally, he doesn't talk to ANYONE. Like sure, he'll talk to his bosses at work and say "hey" if you initiate by saying "hey" first. However, whenever I see him at lunch and dinner, he always sits alone. (Our staff all live on property) and I know for a fact that he doesn't hang out with anyone outside of work on property. He rides his BIKE to a supermarket that is a 20 minute drive away to buy food and cigarettes when our workplace offers staff shuttles to the supermarket. And, if he sees a large group of people, he'll do everything he can to avoid them.

Is he highly introverted or does he just dislike people and doesn't want to get attached? Someone suggested that he may have gone through a traumatic experience and now has trouble trusting people. He is so damn mysterious that I just want to get to know him but it's so hard to when he is so detached from everyone.
Updates
+1 y
UPDATE: So, a few days ago, I finally got the chance to work with him one-on-one and at first, we barely talked and if we did, it was about work but eventually, he started the conversation by asking about the hat I was wearing and then we started talking. Eventually, I asked him why he was always alone. He just laughed and said something like "Why am I always alone? I'm just such a loner" in a very joking manner. He then continued to ask me more stuff about me.
Updates
+1 y
UPDATE (CONTINUED): Overall, he didn't give me much of a chance to ask about him but he mostly asked me stuff about me. I then saw him again that night and he smiled and waved when he saw me and he literally NEVER smiles at anyone (not that I've ever seen). When I see him around property, he continues to act like he doesn't know me and will only talk to me if I initiate... I'm honestly SO confused?
Why is this guy always alone?
Post Opinion