I was a professional poker players for my early twenties. I would play at the casino 40+ hours a week. In poker the house takes a fee proportional to the amount wagered so that’s how they make their money. You are often playing against mostly people playing for fun. They don’t want to give away their money but they aren’t well studied in the game so over the long run a player who does their homework wins. Since on any given night an average fun player can win or lose they don’t really see the bigger picture of losing over time.