given we know that uber increases demand for taxi services ?
Do you have a reliable source for this assertion?If that's the case, then did people stop ridding bikes? Taking the bus? Or did (many) people start using uber instead of other taxi companies because of the price difference (due to uber not paying for all the licenses and insurances other transport companies are subjected to)?
If the later is the case, then regulation exists to discourage unfair competition.
If your answer is by making it dramatically cheaper by externalising the costs of running a sustainable taxi business... then how does having a greater number of people employed on wages that they cannot afford to live on benefit anyone?
Also if you have an app then you will have Internet and could just google taxi + city name
There is an App for it, called "Taxi Deutschland" (how obvious is THAT?) https://itunes.apple.com/de/app/taxi-deutschland/id454467694...
There is even a German wide number, which works in any major city: 22456 from you cell including text service http://www.22456taxi.de/
The app seems to be in German only, and it is of course Germany-specific. I can deal with that pretty OK but not all potential users can. Uber uses the same app for any country.
(Downloading an app local to a country while roaming there may be a rather expensive idea, BTW.)