Why would a guy in his late 30 still be single?

There is a guy I like from who who is 39 and he is single. I don’t think he is married or has kids. But have had the feeling he likes me. But is not taking action. (Most likely because of work) i have given him a few hints that im into him but he doesn’t seem to get it. I was thinking either im not being obvious or maybe he is gay? After all he is a really sweet guy. But definitely masculine and not a typical gay guy.

Why would a guy in his late 30 still be single?
Post Opinion