> some random user cannot make a market

You absolutely can market make on Polymarket. The barrier to entry is actually extremely low; you can do it from an AWS instance in Dublin (the closest non-geo-restricted region to the Polymarket exchange), and don't need the kind of infra that is needed to market-make on US stocks. Retail can absolutely do it on anything crypto-based.

In order to market make, you just need to price probabilities better than everyone else. That's it.

On Wall Street on the other hand it has come down to FPGAs and free space microwave links because fiber optics' index of refraction causes a ~31% reduction in the speed of light. If you don't have millions of dollars you can't get into that game. Over-regulation cas resulted in this space being only accessible to the ultra-rich.