They don't really need to rig their games to profit as you know "house always wins". A lot of user funds are being liquidated into games at the same time. As they have commission for every game that exists, from about 5% to 20% or even more for slots?. As long as users stay active on the casino, they should theoritically always profit. Other than a few freak instances, for which, the casinos have failsafe(to an extent). If a user is winning a lot, most casinos will just shut doors to the user or even confiscate funds if they find anything even remotely fishy. Ofcourse, rigging games would help to profit much larger than what would be otherwise possible but if could get very obvious if the total amount gambled on the casino and their revenue are transparent to gaming commission.