There are inefficiencies that make certain bets positive EV if you are smart enough. It's usually a combination of playing in a weird way and having some insight that the maker of the game (the oddsmaker) didn't see. Gambling establishments don't mind because there are few enough of these and they will ban you if you take too much money from them.
Winning sports betting players often go on to set odds.
Winning sports betting players often go on to set odds.