Earlier quoted context omitted.
Uber has not been successful in Japan for many reasons. 1) the public transportation system is excellent. 2) the taxis are ubiquitous in the major metro areas. 3) the taxi companies have worked together to compete against Uber Japan successfully (Japan Taxi app, etc.)
When I tried using Uber in Tokyo, I was only able to call a licensed taxi through the app, which was incredibly expensive. The one time I actually needed a taxi (in a tiny town in Tohoku) I had to walk around hoping to physically hail one (getting a SIM card that can make phone calls is apparently very difficult in Japan, so I didn't have one).
A pocket WiFi and Skype-Out resolved the issue for me.