But a much easier argument against sports betting is that it ruins the sports. Players throw. They get good at subtly cheating. The gambling apparatus latches itself to the sport, to the teams and players, the umpires and judges, the sporting organizations. With this much money on the line, it's not a matter of if but when games are thrown, cheated -- the bigger the game, the bigger the incentive. It's even easier now because of the amount of side/parlay betting that is available. It exhausts the spirit of competition.
Sports gambling is diametrically opposed to sport itself.
If you, hypothetically, banned it outright in the US, then you go from having few levers on what you can mitigate in the industry to none, because if it's all banned and has more than a slap on the wrist punishment, there's no reason not to charge 200% interest on gambling debts, or other absurd things.
I'm firmly of the belief that the only thing you can really do is tightly regulate it to the point that there's still enough gambling, with controls minimizing as much unexpected harm as you can, to avoid most people feeling tempted to seek out the unregulated illegal avenues with more exploitative arrangements.
I think history has shown that you can't effectively ban a lot of vices, you just wind up with them underground and even more destructive to people involved. The best you can do is try to minimize how easily one can destroy themself - look at Japan's reactive regulation around the most predatory gacha mechanics. Whether you think they strike the right balance or not, that's rather an example of what I mean - you can't really stop someone from deciding to deliberately spend their life's savings on things, you can just do as much as you can to avoid it being an impulsive choice.