Usually casual and responsible players know their loss limit - when they should stop. But since they do not believe in winning, they do not set the same winning limit, although that would be very reasonable. So it seems to me that this reasoning makes sense and it is always good to have two plans - in case of loss and in case of winning.
There are two extremes that usually visit these online gambling sites, those who are barred from real casinos who knows what they are doing and the freaks who does not know when to control their emotions and keeps on rolling even if it means they are loosing, not talking about casuals but these casinos always want these extreme gamblers to make them money, even if they win in the beginning majority will end up busting everything in the end.
Yes, casinos are interested in this, but they are also interested in maintaining their reputation. For this reason, they introduce a variety of programs that help players control their emotions - for example, after a certain amount of loss, access to the casino is closed on that day. This gives the player time to calm down and soberly decide whether to continue playing or not.