why do some online casinos ban you for winning too much

Heard a story this morning from a buddy who got limited by a casino after a hot streak on roulette and it got me wondering about how common this is. I get that the house wants to protect their bottom line, but isn't it supposed to be about chance? It feels off that you can play perfectly legal strategies, avoid any kind of shady behavior, and still get flagged just for a run of good luck.

I'm not talking about card counting or exploiting obvious bugs, just regular play with some actual research and focus. With slots too, I know a few people who were hitting nice bonuses and then suddenly got hit with all these "security checks" or stake limits. Makes you question if skill or pure luck even matters in the long run, or if you're just meant to play and lose. Is there actually any way to protect yourself from this, or is it just luck of the draw whether the casino decides you've had "enough" good days?