Rather than "free", I think what would be better is to allow people to get money back on their taxes for all required transportation done for work, school, etc. So some sort of system would have to be devised to make it so you get reimbursed only for trips that take you to work (and only on the days you work), to school or for grocery shopping (maybe 1x a week?). This forces people to put in the effort themselves, showing the transit "respect" but also enabling people to not be penalized for using public transit to do essential things.