At least with sports betting it's limited in scope. Polymarket applies the same warping influence to the whole of politics and daily life. That's the biggest problem and difference to me, yes it sucks if teams are throwing or players are altering their play to make or break bets but ultimately the effect/danger of that incentive is limited. And with the more limited and well enumerated pool of potential insiders places like the league can pretty easily monitor for it while on Polymarket it's down to open source monitoring and a little blip on their TOS that's nearly impossible to enforce.