I don't think you are taking into account UberPool. HN comments almost never do, perhaps because programmers are generally upper income and do not feel a need to trade money for inconvenience, but UberX is basically a legacy product and now presented as more of an upgrade if you're in a hurry, rather than the default mode.
UberPool is everything. A network of cars buzzing around the city dynamically routing from one task (transport passenger, transport package, deliver food, etc) to the next, and each task is cheaper because it can share ride segments with other customers.
That is where the winner-take-all argument comes from - the bigger the network, the more efficiently Uber can pack multiple tasks into the same driver-hours, with less delay (more jobs means the car doesn't have to go as far out of its way to share capacity).
Uber is more than dispatch - it's quality control, reputation, dispute resolution, capacity planning, payment escrow, (soon to be) routing (it bought a few mapping companies), commercial insurance (try buying that on your own), and increasingly, the efficiency provided by combining multiple tasks in each car.
When people call Uber a taxi service - when is the last time a taxi offered you a cheaper ride if you agreed to share the car for 5 blocks with a guy 10 blocks down the road?
Disclaimer: I used to work there. Throwaway because I'd rather keep identifying information off my personal account.
Opinion is my own, I do not speak for Uber, etc.
I still don't think that most of those checkboxes is terribly important to either drivers or riders. If I were an Uber competitor, I'd thank Uber for screening the drivers for me. Now I can offer them fares at half the price Uber can offer them for. You have a point about delivery, but in the end that's just another fare. There will certainly be good dispatch networks, and Uber may be one of them, but none of them will be able to maintain high margins, certainly not margins that would support Uber's valuation.
Self-driving != Driverless
Self-driving cars is largely a technology problem, and one that we have made great advances in the last 5-10 years. Driverless cars are a legal/social/political problem that we have barely started to look at yet. Self-driving is a driving tool, like cruise-control, but the human driver is still ultimately responsible for the vehicle. Driverless on the other hand places the responsibility for the vehicle, and it's occupants, onto the vehicle itself. Driverless implies that you should be able to use it while you yourself are not capable of operating a vehicle. That is a massive step, and it is something that has never been done before. All other forms of transportation, despite advanced automation, still defers to a human in the end. I would say that true driverless cars is still a significant amount of time away, despite our advances in self-driving tech.