How do CPA offers make money?

I can understand certain niches on how they make money..

Example:

Finance offers - self explanatory
Diet offers, travel etc.. all self explanatory

But for some other offers, how do they make money?

Example, how do the dating niche or gaming niche make money?

1) Resell the leads
2) Premium membership
3) Adsense

I'm assuming they monetize via premium membership most likely.. But, there are so many free social networks for dating..

Is there something I'm missing out here?