Whether they're officially free or not, many people that can't afford to ride the bus in the United States are given free bus passes.
Whilst this sounds nice, unfortunately incidents of drug abuse correlating with homelessness is often in excess of 90 percent. In practice, this means that mass transit is full of puking, psychotic, drug addicts... that frequently are violent towards anyone near them.
This is a politically incorrect fact. There will be some upset with my daring to voice the point. Regardless, the consequence is that ridership on mass transit in the US has collapsed with former users citing safety and cleanliness issues aboard the trains or buses.
Absent some mechanism to address the issue, the mode of transport will be increasingly avoided to it seems the total financial ruin of many of these networks.
BART in San Francisco is in serious trouble and so is is the New York Metro. These systems are expensive to maintain and often operate on subsidy even when ridership is high. Given that ridership has collapsed... these systems will either have to scale back operations radically which could easily lead to a cascading economic doom loop for the systems... or increasingly tax starved cities due to capital flight are going to have to take diminishing resources and increase subsidy to the transit systems.
In "this" context, you want to talk about making the subsidy 100% permanently? Why not. The system is already melting down... might as well remove what lifelines it has left.