Gambling should be seen purely as entertainment. Therefore, whether people make single or multiple bets and win or lose, as long as they view it only as entertainment and don't wager money they can't afford to lose, it's all good. For example, I sometimes make single bets, sometimes multiple bets, and for me it's fine because I only bet amounts I can afford to lose, and when I lose I don't get sad. I don't see gambling as the only form of entertainment; I occupy my time with other things. I think the biggest mistake many people make is wagering amounts they can't afford to lose.
Betting on many games is probably designed for people who see gambling purely as entertainment and can afford to lose the money they wager. In contrast, betting on a single game is often done when someone has strong confidence in the outcome and solid analysis to support the bet, such as in sports betting. Beyond wagering amounts they can’t afford to lose, many people also fall into the trap of chasing wins. When luck isn’t on their side, they tend to engage in “revenge betting,” trying to recover losses quickly, which often leads to even bigger losses.