Most Helpful Guy
Because online-dating is strongly stacked in favour of women. Generally the dating world is already in favour of women as they are the ones being chased after. Online the level of inhibitions I generally lower so girls will get approached A LOT more than in person and thus develop way higher standards than they normally would have.2
Most Helpful Girl
All the guys I've met online said they did ok there. And these were run of the mill guys, not super hot or super rich. They were neither drowning in messages nor struggling with none.
I think online dating pulls in a ton of super socially awkward guys who see it as a potential magic bullet, though. They like that they don't have to do anything but peck out a few sentences to contact a girl, whereas real world approaching is much more nerve wracking. However, many of them still come across as super awkward, with badly taken photos and poor profiles.
I know a lot of super awkward females, too, but it seems like a lot of them don't even bother. They hang out at each other's houses watching movies and ordering pizza.
I'd assume the male sex drive & testosterone's "take action" effects make this difference more likely, as does the fact that young women tend to have a bigger peer group to spend time with.1