I think it'd be a good thing to do. You have a process in place, and enough self discipline to avoid installing such apps. But not everyone is like that. I'm guessing majority of the users go like this: "ah, it's a free app, great, I'll get it. <10 mins in the game, when they run out of gems, bullets, whatnot> Oh, what do I do now? £0.99 is not too bad, I'll just get another pack of <blah>, so I don't have to wait 30 mins".
Can people self-regulate and avoid behaving like that? Yes. Do they? I doubt it.