Probably because I've known some really shitty gamblers and a few who were pretty damn good. A good gambler makes gambling look glamorous, because they've internalized how to minimize their own risks while seemingly playing dangerous hands.
I personally avoid gambling as I'm not good at it. I can see how people do it, but well... just seeing a pickpocket take a mark perfectly from a distance doesn't give you the dexterity and awareness they needed to pick that mark and make the grab without alerting them.
And you're right, for a lot of people, gambling is just being bad at math. But if you're actually good at math(and/or have a team) it can actually be relatively profitable.