You could but the profitability of free2play games are whales. I don't remember where I read it, but the vast majority of people playing free2play mobile or Facebook games never spend a single dollar.

This means that if you set a limit on it, you'd be limiting your profit by an extreme amount.

I'm all for it by the way, I think games that sell game affecting content for thousands of dollars are targeted scams portraying as games to get away with it.

Especially because games like league of legends and path of exile had shown how you can do free2play while only selling cosmetic items, if you make a good game.