It's a thing I've thought about recently - I'm eighteen years old, and I've never had a girlfriend. I have yet to meet a girl I really like. I look years younger than I am and I'm underweight, which means I'm not that interesting either. Additionally, I'm crazy and unpredictable well beyond the point where it stops being cute. It's not so much the idea that I'll never have sex - I could get sex if I looked for it, but that would leave me feeling rather uncomfortable and it would not solve the underlying issues. The main underlying thought is that I'll never be able to get a girlfriend which is, in itself, rather depressing, as that is what social norms - and my own instincts - dictate.
Another issue is that I'm afraid of being alone and exposed in the outside world. It's been a long time since I've been further than a few hundred metres from my house without company from friends or family. I can communicate with strangers perfectly well, and I'm safe-ish in traffic, but I feel it's always useful to have people around to protect me, should that be necessary - and, in that case, the more the merrier. Traveling in groups is my preferred method.
I have one comforting thought, though - most of my friends, many of them neurotypical, better-looking and slightly older than me, have never had girlfriends either. It's certainly not just you, and it's certainly not just me.