But that vast majority of the time, in the US, anyway, the car is used just to get to work and back, not people exercising "freedom of movement".

It seems to me it would be preferable to have mass transit for regular commuting, combined with perhaps some sort of rental system for those times when you need greater flexibility, or need to haul lots of stuff, etc.

That is false. In areas with heavy traffic you can give more freedom of movement. In the typical city without congestion (including US suburbs!), while the car is better, it still doesn't have to be enough better to matter. That you think the car is always better is a reflection on the bad service you have had on public transit.