> Am I missing something obvious?
Considering reports like "Polymarket refuses to pay bets that US would 'invade' Venezuela" [1] one risk is poorly written small print, meaning you might not actually be betting on the thing you think you're betting on. This could also err in your favour, of course - but it's still a source of risk.
There's also the risks involved in cryptocurrency generally - it's the wild west, rife with scams, hacks, unexpected fees, and paperwork.
And thirdly, prediction markets often lack market depth, so if you want to invest a non-trivial amount the price can move a lot. You want to gamble $2,000 to win $190? No problem. You want to gamble $200,000 maybe no-one will take your bet. Can you be bothered to go through all the KYC paperwork rigmarole for $190 ?