The first gas car only had one gas station to use. Progress is made in small steps. We don't have to have the whole framework ready before anyone can use it.
Humans only at the beck and call of self-driving cars who cannot see well in the rain. Instead of "surge pricing" for high demand, it would be "human pricing" to pay for the "skilled" driver in the rain and snow.
ie: $1/mi during sunny days, $10/mi during snow days, instead of $7/mi every day of the year. Very interesting to consider, and honestly a bit scary thinking of so many people I've met who are using Uber to make a living. :-S
Google Maps has a ridesharing comparison function built-in; you don't have to replace incumbents to undercut them when you have the advantage, and the tech will keep improving.