lol. lmao.
No, the "should" should be defined on a performance basis. I'm not enough of an expert to outline a comprehensive set of performance levels that should be achieved, but at the bare minimum, it should probably be cheaper than driving for any arbitrary trip, and should probably usually be faster than driving.
Obviously, investment should be prioritised based on how much good it's going to achieve, but the goal should be defined based on, within the bounds of what's even possible for a society, providing a certain degree of service to everyone.
The "profit" of public transit is measured in how it enables people to live, work, and play. It is the grease that allows the gears of life to turn more smoothly.
This is absolutely one of those situations where capitalism-poisoned brains become self-defeating. Public transit (and a general focus on people-centered infrastructure) means more people going to your business, and spending more money than they could if they were stuck in traffic.
capitalists are the worst at capitalism because they dont care about cause and effect when they get strong enough to force things to be true. it is breathtakingly ignorant behavior in the individual, and in aggregate the teeth of the gears that mulch people and cultures and lands for control
Many estimates suggest things such as proper universal housing, healthcare, and even a UBI would decrease costs and increase spending. (Since you could then regulate those things, decreasing wasteful spending, whilst stimulating the economy.)
When your workforce is housed, fed, and healthy; and when you aren't having to drop millions of dollars in company money on expensive insurance programs or benefits; and when your workforce has the income to not live paycheck to paycheck (or worse!); it turns out you can make more money.
Capitalism is like the "paradox" of tolerance. It doesn't work if you go 100% in on it. Gotta throw some socialism in every now and then to keep it functioning healthily.
Realistically, capitalism should die off, but it's amazing just how bad at capitalism most major capitalists are, just by failure of understanding holistic budgeting and long term planning.