Honestly, it's not all that different from something like the Play Store. There's a LOT of games that are trying to get people (who don't know any better) to spend money. But there's also a lot of real quality games, too. Many of the best games have the option to spend money, but don't shove it down your throat.

As an example, I played Bee Swarm Simulator with my daughter and I really enjoyed it. I decided to buy some robux and spend it on the game.I did this not because it gave me something I needed to enjoy the game, but because I felt the developer deserved it for creating something that entertained me.