The OF site employs psychological tricks to draw you in and keep you there. Casinos and pay-to-win video games use similar tricks.
One example is, mixing free content with payment-gated content at a very small fee. A lot of people think, "meh $2 isn't much - I'll pay $2 to see this one pic" and that money adds up.
It's life on easy mode for women, to be sure. But don't take it as too much suifuel. These women have a short time in the sun. When they get old the money will stop coming. And like everyone else, they're going to be old for the majority of their lives. They have maybe 10 years of being hot (maybe, if they have good genes) but they have 100 years of life.
What actually makes women happy for the majority of their lives is family. And these women are foregoing their opportunity to have that. They might make a million dollars or even a few million, but they wont invest it (because they'll assume it'll last forever) and having the money will prevent them from loving any normal man who isn't rich. They aren't hot enough to pull a rich man, so they're basically doomed to be alone and unhappy.