Poor and elderly people, for a start. Spend a bit of time by the entrance to a major hospital and observe how the other half uses taxis as a lifeline; you might just change your tune.
It may come as a surprise to many people here, but taxis aren't just there to transport privileged rich folks to and from parties. They're an integral part of any well functioning city's transportation system, and handing the keys over in the name of disruption is naive at best and outright dangerous to some of society's most vulnerable populations at worst.
Disclaimer: as a card carrying member of the privileged elite, I've used Uber in the past and will probably do so in the future. I'm merely trying to point out that the taxi industry doesn't exist in a vacuum.