No matter how good public transit is, it will never fully replace the need or desire for cars. Especially now that self-driving cars are hitting the scene. There will be routes poorly served by transit, people hauling stuff that can't be easily taken on a bus or train, people who prefer privacy, stuff being transported by truck, and people who just like road trips. These people are all still imposting a cost on other drivers by driving (when there is congestion). I haven't yet heard a good reason for why that should be free, no matter how good public transit is.