It’s just because it’s convenient. I’m not at all surprised that, first of all, fast online games became super popular, since everyone likes quick and simple gaming content and content in general. Second, gambling is something that in just a few seconds lets you feel a bunch of emotions. Claim your bonus if you want to make the process even more intense. Playing through bonuses makes you doubt, worry, fear you won’t make it, fear you’ll lose money and the bonus itself. All of that causes a storm of feelings and emotions, and that’s exactly what people want.