Communities address shared problems with cooperative solutions. Examples abound: schools, roads, policing, fire services, water-treatment, libraries.
These common necessities are wholly or partially funded from general tax revenues. This is acceptable because each is considered to be a "Public Good". We do not expect them to "pay their way".
Over the past sixty years our society embraced the automobile so fully that rural transit systems fell by the wayside. This has left significant numbers of people who don't have access to an automobile with difficulty getting to work, to secondary education, medical appointments, shopping, or enjoying fully the social and recreational opportunities available. We have conveniently ignored them, at social cost. Additionally, lack of mobility is a major factor in migration from rural areas to cities.
As costs of fuel inevitably rise, those with marginal ability to operate a vehicle may be forced to consider moving to urban areas unless public transit can provide a practical alternative. In some cases even infrequent transit service would make a great difference in the citizen's life.
A transit system, therefore, should be considered a public good, and eligible for some subsidy. In fact, as we see here, all transit systems stimulate significant economic benefit.