Some of this has been mentioned before. Credit to those I am repeating, if I do.
Here's the "Reader's Digest" version of why I think it's difficult to meet women on here. In no particular order:
1. Many girls on here are taken.
2. Some girls on here are not girls, and won't meet.
3. Single girls are vastly outnumbered here. They can take their time, have their pick of us, and as a result, tend to have higher expectations. They can, and it is what it is.
4. Some girls don't believe that the internet is a viable way to meet a partner. Deception is often involved, and distance is often a major factor. I've been in LDRs twice, and they require a lot of work and some luck to become long-term.
5. Some girls are lesbians.
6. Some people may have confidence issues and not believe they are worthy of a relationship.
7. Some girls have been burned, either online or IRL, and are not ready to jump in to things again.
8. Many guys on here just come off to girls in what seems to be a weird way. You have the creepers, too anxious and forward in chat or in PMs. You have the overly-polite ones. You have the ones who gush at every girl who posts a pic. You have the guys who project confidence issues. You have the guys who show implied creepiness -- threads like, "tell me what you'd do to me", "tell me what you'd like me to do to you", and "I asked a celebrity what her shoe size was and if her second toe was longer than her first!". I don't mean to be harsh, but I read these threads, and I know these things wouldn't go over well in a bar or bookstore. There's no reason to expect they'll go over well here. These experiences make women wary, as they should.