Uber is a great concept, but the reality is that Uber has shown us time and time again why taxis cost what they do: regulation to protect users and our cities.
Uber, like AirBnB and a lot of other startups, are 'disrupting' industries by entering them and taking them over by ignoring regulations, insurance, and even laws to keep costs low and make a profit. In this day and age, they can grow fast enough that by the time cities see the repercussions and react to them, the companies are big enough and rich enough (and flush enough with VC money) to fight back, and are already entrenched with a loud and enthusiastic user base.
In other words, Uber is great if you ignore the various safety and insurance regulations, background checks, licensing, etc. that taxis have to comply with.