Not sure I agree. Whatever reason the city has to allow cabs on market should equally apply to uber or other mass transit. The reason they want to allow cabs could be because it optimizes transportation for the residents of the city if there is less car owners and more shared vehicles. That would apply to uber as well. It could alternatively be that the city believes professional drivers (those that do it for a living) are safer drivers than the average car owner. This would apply equally for uber as well. I can't think of a reason that the city would want to allow taxis but not ubers to use market.

In fact the only thing I can think of is that the city actually supports the crazy medallion monopoly we've built which is insane.