Taking drunks off the road, providing carpooling options, reducing need for parking, making it possible for for people to not need cars who are on the fence about buying one, frictionless payment options over cash, eliminating "zoning" by different cab entities that block off under-served neighborhoods. There are plenty of positive externalities to Uber too. I don't know about you, but I'm old enough to remember when cabs sucked and you dreaded it or considered risking just driving yourself after a night out. Uber made things easier, better, and safer.