I had friends who used to play online poker in uni. They’d have 5 or 6 screens open at once and just play the dominant strategy for each hand. Was good for some extra beer money.
Also work with a dude who is a former professional poker player. Although when he explained his schedule to me it sounded a lot like a regular job. Good years he could make £40k out of it but not crazy money.
With poker the house takes a “rake” from each hand so they get a certain % of whatever is being gambled for hosting. Since the game involved skill they have to do this to ensure they are making money regardless of who wins.
Pretty much every other game is like you describe; people being bad at maths and conditioned to keep going with inconsistently timed rewards.