Fixed-route 19th-20th century public transportation networks are inefficient because most of the vehicles are pretty empty most of the time. This makes these systems expensive on a passenger-per-seat-mile basis. Not to mention the colossal waste of people's time spent trying to accommodate their journeys to those fixed routes (and schedules).
Example: LA's Metro system is subsidized to the tune of about 50 cents per passenger seat/mile, or was as of 2009 (http://www.newgeography.com/content/002361-los-angeles-metro...)
In 10-15 years, transport companies like Lyft/Uber/Didi will be able to offer municipalities a much better deal than that. An electric car or van without a driver in it, with an operating lifetime of a million miles, will cost on the order of 20-40 cents a mile to run. Get 3-8 paying customers into the vehicle, and there is absolutely no need for a 50 cent per passenger seat mile subsidy.