Not only slot games but also other non-slot games are risky and gamblers can lose money because their bets and chances of win or lose depends on randomness, probability and luckiness. All of those contributors, but there are more ones, can not be controlled by gamblers so the risk of win or lose with bet is very uncertain.
We need to be careful playing gambling games. We never know when we win or lose. But the losses will be behind us after we start gambling. If we can be careful, there is nothing to worry about because we can take care of ourselves and avoid mistake. We will not follow our greediness but we control it and not ruin ourselves.
Understand about bankroll management is good fundamental for making your bet strategy, then bet action, but you must control your emotion, psychology and bet capital management too. Most gamblers fail to control themselves so even they have knowledge, they often take too high risk by overgreedy and lose money. It's not responsibility of casino or any game type, just uncontrolled actions from gamblers that increase their probability of loss.
If gamblers fail to control themselves, they should learn more before the same thing happens. If they think that they lack control, they must be strict with themselves and always be aware and know when they must stop gambling. They can not continue gambling if the situation almost changes and it is better to stop gambling and calm down their minds. The risk will become higher if they keep gambling because that can affect their minds and cause them to forget their rules.