"Labor," huh? Uber's "laborers" also carry the capital cost, operating cost, and risk of the transportation service they provide. They own their vehicles and pay for fuel, maintenance, and insurance.

Who covers those costs when no drivers are in the mix?

Somebody has to pay for that stuff. It's still true that a big chunk of uber's success in big cities comes from dodging regulations and medallion costs. In other words, they are gypsy cabs with a slick app.