When you're winning, the casino is losing, when you are losing, the casino is winning.
The thing is, they wouldn't limit you if you just win a couple of games, but if you are staking high amounts and winning continuously on the spin, they have no choice but to limit you to a certain amount, that way they reduce your payout if you win and their losses in the process. That being said, if you break any of their rules, you're going to be banned and the next action your friend took is against their rules, so he can't have too many complaints.
Of course, the aim of the casino is to make a profit from the large number of people who gamble, and with those who may gamble continuously, especially using high betting amounts, the chances of winning are big, but the chances of losing are even bigger, and what you say is true, of course, if the gambler can Winning continuously of course will not be allowed, of course the casino will limit or even take back the winnings that the gambler has earned, also I think if they can win more than twice it will actually make them continue to gamble because they feel confident that they can get even bigger wins, but of course the casino will not make them win in the long term because that is not the goal of the casino, although there is indeed a chance to get a win but of course the casino will limit the wins that the gamblers will get so that their casino keep going.
Apart from that, I don't think any gambler can win consistently, it's very unlikely that this will happen to those who are just ordinary gamblers even if they say they are professionals at gambling, I don't think they can win consistently if at all. There are people who can win consistently, maybe they have made gambling their main source of income, but considering gambling as their main source of income is wrong. because it could lead them to big losses.