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Most people enjoy betting on sports events or gambling only when they win, of course, if they are not fans of the sport (they bet for fun) or gamble only for fun (such people are very few).
Betting on sports allows the bettor to use a wider analysis than any gambling games, so the probability to earn by such activity is higher than by gambling.
That's true for almost any other game. Nobody loves to play a game which they always lose. If people can make more money from sports betting, they will like it more than dice for example. If they were making more on dice, then it would be the opposite.
I agree that some people love sports because it lets you to do research on certain stuff about the teams. That's not possible for the luck based games. Maybe it is this research process which makes sports betting more appealing...