The success of Didi in China has been interesting. They have largely co-opted the taxi pools in Beijing/Shanghai/Shenzhen by allowing you to bid/pay the driver to pick up riders. It has changed dramatically in only a few years.

Although locals tell me it is illegal you can wait over an hour and a hundred green-lit taxis before one will stop to pick-up someone without an app that is willing to bid a few yuan. Train stations and airports have cues where you can still get a ride, but don't count on hailing a car in the evening even in a busy downtown district.

As a result they control all of the taxi business and all of the ride-shares. I must say not having to transact in cash is nice.