When I go to the supermarket, I get one price for bananas and my friend gets that same price. I don't pay 1 dollar while he pays 1.10. All the customers have the same pricing. This is the key difference.

If every customer has a different price, like Uber does, that opens up pandora's box. Naturally customers will start wondering about patterns and what they can do to lower their price. They might speculate if people of race X are given a slightly higher price on average, or what other physical characteristics might play a role.

Your supermarket doesn't play that game.