You make it sound so easy. The first issue is, taxi licences are super expensive. Don't get me started on cities that deal out medallions at ridiculous prices. In New York a taxi medallion will cost you about $1 million, how ridiculous is that? The system itself is broken and outdated, currently the system is engineered to benefit the companies selling medallions and those other bolt-ons that come with owning a taxi.
However, I do think that Uber and other services should honour pricing caps in cities that have them, they should also comply with rules regarding insurance and other reasonable things asked of them. But having said that, even if they were to honour pricing caps and get the appropriate insurance for their drivers, it will never be good enough for some cities, take Vancouver as an example.
In places like New York especially, too many people benefit off of the existing cartel like structure of leasing out a medallion, insurance and all of the other costs that tend to add up quite quickly. Things need to change, and I am glad there are companies out there pushing the boundaries and getting the conversation going. Gone are the days of a single company having a transportation monopoly in a city.