Casinos love martingale players. It's also a myth that minimums and maximum bets are there to prevent Martingale.
Minimums are there because casinos consider bets that are too small to be a waste of time considering overhead, and maximum bets are there because the variance is too high for the casino to handle.
I've never heard anyone claim that casinos set their maximums to prevent martingale. Only that martingale is prevented by maximum bets (i.e., all keyboards have keys, but not all keys are part of keyboards).