it's true that public transportation has a net societal benefit, and that portion of the benefit should be paid for by all (through taxes or whatnot). however,

it's true that public transportation has a net societal benefit, and that portion of the benefit should be paid for by all (through taxes or whatnot). however, fares shouldn't be zero. riders should pay too, not just because we should bear our portion of the direct benefit (we should), but also because it gives us a sense of ownership for the system. those fare revenues give transit agencies funds to improve service, and riders legitimacy in demanding better service. public transit needs to get better in every dimension: frequency, timeliness, coverage, capacity, cleanliness, etc.