But, as bankroll of the house is in general bigger than an individual player, they manage to keep the bank rolling in the long run and hence make profit.
Let's say a player has 1 BTC, and the casino has 1000 BTC. With a 0 house edge, the casino has a 99.9% chance of bankrupting the player. And the player has a 0.1% chance of bankrupting the casino. (Number slightly rounded). In other words, the casino is risking absolutely everything for no expected profit and negative expected bankroll growth (given enough time, someone will get lucky and bust the house).
I don't expect that a rational casino, that understand the risks will ever do this. 0% house edge gaming has potential, but I think strictly within a pvp setting.