If the differentiating factor is just who you’re betting against, how are Kalshi et al any different from online poker? It’s still gambling, the house just takes a rake

I agree that whether the house has a stake in the outcome is (probably, I haven’t read the statute) not relevant to the definition of what is and is not gambling under Utah state law. Online Poker is very obviously a game though in a way that Kalshi and online brokerages aren’t (even if they share game like elements, such as random rewards). Important to caveat that prediction markets do allow you to speculate on the outcomes of games occurring off the platform, and maybe that is the distinction here between Kalshi and Robinhood, but then is Kalshi still “obviously” a gambling site if they ban markets on sports outcomes but leave everything else?

Because you can easily collude and cheat at poker so it needs to be heavily regulated or outright illegal to prevent theft. You can't really cheat at prediction markets, unless you have insider information which they can litigate after the fact.