It's one of those things about the way Americans think about transit that makes me insane, they try to assess the ROI of every single individual leg of a transit system rather than assess the system as a whole.
For example they'll cancel late night bus service because very few people use it. Except that the people who do, are people who occasionally are forced to stay late at their job and rely on the bus running late. Once it's cancelled they have to drive to work every single day since they're not sure they won't be stranded. The 3-4 bus rides a month they used to take are exchanged for 22 private car trips because you cut back service.
That's just one example. Here's another more suited to your example. What if you generally switch to taking transit into the city, and only take an uber when it's raining or you have something heavy to carry?
If I allow there to be a robust market for Ubers in the city then that's possible. If I aggressively charge Ubers then you can't do that, and you're back to driving every day.
There's plenty of examples. But in short it's clear that private cars are by a mile the worst and most inefficient thing occupying the roads. That's what we want to have the strongest incentives against.
