Your bus shows up on your doorstep on demand and will go wherever you want it to go? Your taxi will drive you for two hours to see your parents, then wait around for a few more hours to take you all to the beach and only charge you as though you're the car's owner?

I've seen it argued that in TCO terms the taxi (well, two taxis in that use case) is cheaper for that.

Perhaps, but add to that all of the incidental trips to the store, to visit a friend, to go to the bank and so forth and it probably starts to level out a bit.

emmett was talking about efficiency, safety, and the ability to travel without having to drive. You're talking about convenience, which is an advantage to cars (self-driving or not) but self-driving cars still can't deliver on efficiency, are still less safe than most forms of public transit, and have greater expense.