Taxi laws are a
government subsidized monopoly for old world Taxi companies.
You don't need a special license to pick up extra passengers so you can use the HOV lanes during the Pan Am games, do you! The government is FORCING you to carry passengers so you can efficiently use the roads YOU paid for, or you get a ticket!
So why do you need them for Uber? Besides a hundred years of corruption and protectionism for Taxi medallion holders.
There is NOTHING different between the functionality of any ride sharing app and putting a sign on a company bulletin board asking for riders; besides the form of communications being used.