What about bets without insider participation, where you want the market to function as an aggregator of educated guesses? OP has one reaction to insider trading, but I imagine a very common alternative would be "those insiders make their money off of bettors like me, I shouldn't participate." Some questions are clearly insider-proof, but I imagine many questions have insiders who don't bet on Polymarket. If Polymarket is going to be a good prediction market, surely it should incentivize people to make predictions on those questions too?