You’re making an error in your analogy.
When I sell you my Smurfs collection on EBay, I set the terms of sale and you bid. You and I come to agreement on the terms of the transaction, within some limits that EBay, as the platform, sets.
When I sell a ride to you on Uber, Uber sets the price, tells me where to pick you up, and even dictates the route I should take. I don’t even get to see where I’m taking you until after I accept the ride.
On EBay, you and I are negotiating with each other. On Uber, the driver has no say in what the offer to the passenger is.