In short, these games try to get people to pay cash for in game currency so they can level up faster and have a better overall experience. Which is fine. But for users who won’t pay cash, a wide variety of “offers” are available where they can get in-game currency in exchange for lead gen-type offers. Most of these offers are bad for consumers because it confusingly gets them to pay far more for in-game currency than if they just paid cash (there are notable exceptions, but the scammy stuff tends to crowd out the legitimate offers). And it’s also bad for legitimate advertisers.
I really enjoyed this post by Michael Arrignton on Tech Crunch. Technically the online gaming companies are the same as "respect points" apps.