Exactly. I see this common idea trotted out that "where there's a will, there's a way" -- if the government bans something, the ban will never be effective, because people still want that thing, and so a ban will just encourage violating the law.

But that's highly contingent on that thing being something people are willing to violate the law over, and on the convenience of that thing not being significantly impacted by prohibition. Neither of which are true for prediction betting (it's almost identical to sports betting in that regard, imo.) The only reason these markets proliferate is precisely because they are legal.