I'm 26, I've only dated once, for 3 days. It was kind of not serious, lol.
I'm definately not unattractive, personally I think I'm handsome, and I've had plenty of girls chasing after me over the years. I just don't indulge them, nor do I particularly hunt for girls myself.
And that's my main reason for still being single I guess. I don't go in for it, and I suppose girls are somewhat scared to approach me with their feelings because I never flirt or answer to flirting, barely talk about relationships, rarely sex and never about women in the way most guys do. I actually find such conversations to be tasteless and stay out of them. Also I'm a bit eccentric and distant at times, but I'm good company and most people like me.
In fact when I think about it, most girls I've ever gotten close to have fallen for me.