Prediction markets can only do sports gambling (the vast majority of their volume) because they self-certify under the CFTC. The CFTC doesn't have the same standards of "insider trading" as the stock market, because insider trading is the entire point of business at the CFTC!
If you're trading, like, oil futures or wheat futures or whatever, you are likely doing so specifically because you have inside information about your business needs or production that you want to hedge.
I understand why people are mad about gambling versus someone who has insider information, but under current US law I'm not sure that there is a case to be made.