yeah it's true, most casino doesn't have restrooms inside the buffet, they actually want you to walk out to the casino floor and find other alternatives. It another simple strategy alure you to gamble more, and want you to see what's other guest are doing beside eating. So by the time you are back to your table, you want to finish up and go for a gamble.
Same strategy as no clock on the wall for you to know how long you been playing, and also all drinks are on the house, you can get drunk all the way, so they can take more of your money. Casino is a form and a place for entertainment, where they hire people to think, strategize and plan the best way to server while taking from you. so there'll not be a restroom in the buffet, and they can careless how many time you are in and out of the place. as long you stay to gamble.