I actually agree with you. They could operate completely outside the boundaries of the airport, in which case they would not have to pay the use fees to the air

I actually agree with you. They could operate completely outside the boundaries of the airport, in which case they would not have to pay the use fees to the airport. The problem is that part of their value prop to customers is that they offer airport pickup (they send a black car to bring you from the airport to the rental agency). This puts them in a position where the airport has a right to demand use fees, since they are using the same roads and infrastructure as any other rental car service. Reducing costs by not using the infrastructure, and therefore completely circumventing the need to pay the use fees, would be disruptive. Using the infrastructure but refusing to pay is not disruption. They are not doing anything more efficiently, they are just refusing to pay. This issue should be understood as completely distinct from their core car-sharing business model, which is disruptive to the rental car industry.