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.
There's a false dichotomy between prohibition and laissez-faire, which the US seems particularly prone to. You've seen similar issues with the decriminalisation of cannabis, where many states seem to have switched abruptly from criminalisation to a fully-fledged commercial market. There is a broad spectrum of other options in between those points that tend to be under-discussed.
You can ban gambling advertising, as Italy did in 2019. You can set limits on maximum stakes or impose regulations to make gambling products less attractive to new customers and less risky for problem gamblers. You can have a single state-controlled parimutuel operator. Gambling does cause harm - whether it's legal or not - but it is within the purview of legislators to create a gambling market in which harm reduction is the main priority.
> You can ban gambling advertising, as Italy did in 2019
this has been widely sidestepped, betting companies now advertise something like "sport-results.com" and then that one has a prominent link to the betting site.
I hate it though the legalisation, especially since it turns out:it is as bad as they thought it was, no the companies do not do the required addiction checks and yes it ruins people's lives.