For the same reason a lot of marketplace regulation exists in effective societies where markets are key to economic functioning.
A good marketplace develops consumer trust. Parasites will try to exploit that, creating bad experiences and diminishing that trust. But that is bad not just for the consumers getting scammed, but both the marketplace and society at large. It's also bad for society to have lots of money ending up in the hand of criminals, because they will then go do more crime.
And note this doesn't stop you from doing business with Joe Anonymous. You just can't do it on an online marketplace. But you can always just not look at the details if you want, so you can get the experience you seek with a little custom CSS.
If you don't want to buy from Joe Anonymous, that's your choice. But if I want to, why should the government prohibit it?