There's always a catch.

According to an October study by U.S. Public Interest Research Group (U.S. PIRG) and the Frontier Group, millennials are driving significantly less than older Americans.

It is likely that these services will just exacerbate the differences that already exist in the quality of public transit in different areas. The localities that invested and ran their systems well won't be as impacted. In the areas where frustration is higher, the problems will surely become worse when revenues and ridership decline.

Imagine how much money could be saved, and how much traffic and pollution could be reduced, if people shared taxis with strangers.