You have a point, but still, if you are well-experienced in sports betting and you confine your gambling scope to certain options, you are better off, as you can win more, appreciate your skills and be proud of your decisions, and can be consistent as well. Can you say that about casino games? Heck no! Casino games are not a respecter of how brilliant you are, nor the skills you've gathered to play it, the house reigns supreme, and they only let you win when they want. You are playing against certain algorithms here that "you cannot beat," you can only be lucky to be happy with it. This is unlike in sports betting that you and the house have a 50/50 chance, as they do not have any influence on the outcome.
By mathematical and probabilistic law there are more options to win in sports betting than in a casino, in fact I don't know the probabilities, but I'm sure they must aim for it, you can't win more in a place where the house advantage influences 100% than in proactive bets where you win by knowledge, of course you can lose, but it is by knowledge, that is like saying that in trading the opportunities to win are the same as in gambling, you have to be clear about that.
The popularity of sports bet is increasing more than casino games and I believe that it is because gamblers have higher chances of winning in sports than casinos. The house edge is more pronounced in casino games, they set all the rules and you will play knowing that you are relying on only luck to win, also knowing that you don't have a fair chance to win. In sports bet both the gambler and the bookmakers don't know exactly how a game will end and that gives the gambler an edge to win compared to casino games. The chance that a sports bettor has to make sports analysis is what gives him an edge over the gambler that totally relies on luck to win in a casino.