Mmorpg games and parental control.

The thing is mmorpg games are really addictive and make the new generation of children loose their study time on those kind of games. Nowadays there's internet in every house and mmorpg games tend to be free to play so they are accessible to anyone, even kids. So to prevent this it should be implemented some kind of parental control. My idea its easy. In the registration of the game it should be asked a symbolic credit card payment (20 or 50 cents for example). Kids don't have a credit card so to do the registry they were obliged to ask their parents to do the registry. In that registry their parents could specify how much time their kid could spend daily on the game and have an option to change this whenever they want. This is a simply way to make sure that your kid is not spending 6 hours/ day in a game instead of studying.