Why do casinos limit or ban a user when he or she is winning too much, but do not do the same when the user is losing too much as well?
Just as someone already said here, casino is a business for another man and the person only makes profit when the gamblers are losing their bets or stakes and there's no way a casino owners will discover that they are usually running losses due on one customer that they will not want to kick the customer. The house edge of the casino games is already designed to favor the casino and not the gamblers and if the gambler keeps winning, the casino will have no option but to either restricte the account and if you are not lucky enough, they could say you are using a Bot (lol) just to make sure they tag you to something allegedly.
Yes so obviously one of the reasons why casinos do not limit the number of defeats of the gamblers who play there is because the goal since the beginning they built the casino is to make a profit and the profit is only obtained from the losing gamblers, meaning that when more and more gamblers lose then they will also be happier, and that's why casinos often do promotions by promising something that sounds very tempting, none other than that just to get more people interested and enter the trap that in the end they will most likely lose a lot and the casino gets a lot of profit.
So I think it's unlikely that casinos will limit the number of losses of gamblers while profits are the top priority, on the other hand I have never experienced the incident described by the OP because I have never had such a big win, but certainly limiting the number of winnings of gamblers yes maybe it can be done by casinos because there are no other options to avoid bankruptcy, but yes anyway I would say that the casino is irresponsible.