Polymarket isn't a stock or commodities market. There is no underlying value to it. It's zero-sum: the only money coming in comes from the other players. (Minus their overhead.) It's gambling.
It's bad enough that desperate people can lose everything gambling. Leverage allows them to lose more than everything, and that seems like a recipe for disaster.
I don't want to just waggle my finger at prediction market gambling. If that's how people want to spend their money, it's not up to me to protect them. But having the market itself encourage people to spend more than they have seems more like greed than like a serious consideration of market dynamics.