On a site that men pay but women join for free you're going to find a lot of women who expect men to pay for everything for them, and the only men on that site are going to be the kind who expect to get what they pay for.

Now, I'm not saying there's anything wrong with that, everyone's a grownup after all. But that isn't the demographic that match.com et al are after - they measure their success in how many marriages they produce. Marriage-oriented people are also more likely to be at the point in their lives where they have money to spend to, they're a highly desirable market.

The more people on the site who live near to a user, the more likely that user is to find someone compatible with them.

Having said that, "quality" might be important if it's a way of making it likely that users are more compatible with other users, e.g. religious-minded people who want to marry within their religion.

This hasn't really stopped men from trying, though. The gender ratio doesn't have to be perfectly balanced, all is has to be is not ludicrously out of whack.