Ages ago, a friend of mine who'd lived in Las Vegas for a number of years told me about a bet he nearly took. All you had to do was to bet that a football team would have about an average level of performance during the upcoming season and you'd win. If that team later went on to the playoffs, you'd make even more money, and if they made it to the Superb Owl, you'd make even more (regardless of if the team won or lost). He declined to take that bet, and a short time later, he read in the local paper about how the companies that handle sports betting do it. They have a bunch of computer programs that study various things like injury rates of players and how they impact the game. So, for example, they'll figure out that a team can play five games without a significant injury to a player that will impact the outcome of a game. So they'll offer a really good bet that a team will win six games in a row before losing due to a star player being injured and unable to play. Sure enough, one of the players on the team had an injury and couldn't play, so the team started losing enough games that there was no way my friend could have collected on the bet had he placed it.
I'm sure there are plenty of people who make a living betting on sports. The problem is that if you're going to be a consistent winner you're gonna have to do shitloads of work. I watch sports for enjoyment and escape, which conflicts with the idea of doing the work required to be a winning (or at least "break-even") bettor.