[shadowgovt]

Unlike buses, this has a chance to pay for itself.

[fnord77]

Why should public transit have to pay for itself? The downstream economic benefits of mass transit are enormous. Expecting transit to break even is a recipe for poor service

[shadowgovt]

But the original question was "Why can't we just invest in buses?"

And that's the answer. Who invests in something with negative ROI? (Which is, indeed, why so many mass transit systems are taxpayer-supported).