I do not think there is too much of a point to think if it is fair or not, it is just the way it is and if you do not like it then you can avoid paying in a casino.

However now that you bring the point casinos put those restrictions in place basically because of two reasons, the first one was that back in the day hackers used casinos to deposit their coins in the casino and then get other coins, this was done as a way to erase their tracks, so casinos now force you to play a certain amount of time with your coins so they know that you are not just trying to use them, the second reason are the bonuses, casinos give money away to attract players but without those requirements some players will abuse the system and eventually the casino will be unable to keep their doors open so they need wage requirements to avoid that.