Sports teams don’t want it because it incentivizes cheating / rigging games.
this isn't true generally speaking. The reasoning they give is that gambling has always been there to incentivize cheating/rigging, but at least now it's out in the open and easier to track. This is a quote from the commissioner of the NBA after an incident last year:
“I mean, this is not new that there’s unsavory behavior, even illegal behavior, around sports betting,” Silver said. “I guess my point is that to the extent it’s going to exist, if you have a regulated environment, you’re going to have a better chance of detecting it than you would if all the bets were placed illegally.”
Sports leagues are tripping over themselves expanding into Las Vegas. Some team owners have their own sportsbooks right in the stadium, for example ted leonsis in DC. The owners of the Dallas Mavericks own the Sands casinos and have been spending millions lobbying to legalize gambling in Texas. (edit: I see their efforts recently failed, but the point is they clearly want gambling.)
Some individual players have spoken out against sports betting and if they were the majority they could take it up as an issue in collective bargaining. NBA players did in the last CBA, except they went in the opposite direction; they negotiated for the ability to endorse and invest in gambling companies themselves. So clearly the majority of players are happy to take bigger contracts, endorsements, etc despite the nuisance it causes them.
and to be clear I agree it's awful, i am just explaining how i observed them deal with the issue over the last 7 years or whatever. I actually recently stopped watching sports, and sports betting was a contributing factor to that decision.
