You must live in an area with good to great taxi service.

There are areas where taxi service is so spotty as to be scary, were simply getting a cab is a huge pain (IE: called and ordered) and flagging one down is a non-starter. Even after calling in a cab, they often end up being no-shows (get a better fare en-route, etc)... it is scary when you can't get dependable public transit home from a location (stuck alone, outside, waiting for sometimes hours).

Uber started and initially flourished in areas were taxi service was insanely poor due to bad regulation and/or corruption. Uber was basically a response to the godawful taxi situation in SF.

I know I feel far more comfortable when the people I care about are able to get an Uber/Lyft/(similar) service.