It’s not that hard to look at lines at Pinnacle and Circa and make estimates about the fair value of a wager. Open accounts at every book and line shop and maximize expected value.
Also you are ignoring platforms like Novig which are like the polymarket for sports betting.
Betting platforms specifically work to identify customers who act in such ways and ban them from the platform. Developing accurate odds costs money, it's cheaper to just identify "advantage bettors" and ban them.
I'm not sure this applies to these prediction markets. Normally when gambling you're at a casino playing e.g. blackjack, where if you're winning more often than expected you're taking the house's money.
But this is more like playing poker, where overall the casino could care less if you're continuously crushing the other players, as long as people keep turning up to play and they keep getting a rake.
There is no comparison. A quick search about Pinnacle: https://www.reddit.com/r/sportsbook/comments/kek5t8/warning_...
My experience (though I have never bet on these platforms) is that Pinnacle-like platforms almost never let you withdraw your "earnings". They are essentially a bookie.
Polymarket on the other hand, is just an exchange. And they use Defi to make sure you can always withdraw your bounty even if you get "front-end" banned from their platform.
So to affirm the previous poster: These companies are not in the same business.
They absolutely let you withdraw earnings. I place around 20 wagers a day. Pinnacle and Circa are used as measures of what the market is actually pricing in. You can devig lines to arrive at event likelihoods. From there you can line shop such that your expected value is positive over the long run.