I think you can make an analogy with Casinos and their incentives to cheat. They could do all sorts of things and there are plenty of gambling scams that do those things, but most legit looking Casinos are already making money hand over fist, have published odds on their favour and against yours, can kick out anyone who seems to be doing well, have all sorts of non-cheat tricks to squeeze money out if you, and are risking serious reputation and legal damage if found out.

Doubtless there are scummy poker games, but for most of them the money comes plenty easy, and the existential risk of faking cards to increase pot sizes just isn't worth the marginal benefit.

Of course everyone, winners, losers, and impartial bystanders will see these patterns in completely random deals so every site will be accused eventually.