Yes, I can think of a reason: that's life.
I'm not being flip. I get questions like this at least ten times a week. "Why aren't guys asking me out? Why do only creeps and jerks ask me out? Why don't the guys I like ask me out?" It is a common refrain. The answer is that this is just how dating is--kissing frogs and all that.
The only other reason could be that you have a repellent personality, but if that were the case, I think you would know it. I don't think that's the case. I think this is just how dating is. Keep sifting. You'll get lucky sooner or later.
Thanks for the question.