Old age
minor disabilities (for major ones we do have some mitigation)
cold
heat
rain
snow
cost ( electric bikes and golf carts are $$$$)
Personal security and safety
Need to carry heavy objects like food
Reality (auto drivers do vote)
etc.
And I'm an advocate of good rail and bus service
Also, notice that the original poster also included "micro-mobility transit" in the non-car options. I guess this could be stuff like on-call minibus, Uber, or even Zip-car-like golf carts parked in the neighborhood that would allow subscribers to get a ride to the nearest real transit stop.
These sort of things would overcome most of the objections listed here.
In any event, the people who have real physical problems that limit their ability to walk are a very small minority, and, yes, they could be accommodated. That's why we have "handicapped" parking spaces. Maybe in the New Urbanist utopia, tha will be the only type of parking spaces available. May people who **think** they can't walk are merely out of shape or believe that walking is beneath their dignity.
"Personal security" is an overrated issue in most of the country. Most people run around scared of muggers and such because political demagogues and news outlets interested in goosing viewership via sensationalism make American cities appear much more dangerous than they really are. There are exceptions, of course, but the people living in those areas are less likely to be able to own a car, anyway.
In a real New urbanist utopia (or even a modern central city), stores are located close by, and you do shopping more frequently than in the 'burbs, thus not needing to carry large amounts of shopping parcels. In any event, there are shopping carts that look like wheelie suitcases that have been used for years that allow people to easily transport several full grocery bags home from the market. I know, I've used them when I lived in Center City Philadelphia. We had a car, but we really didn't need to use it much for day-to-day mobility.
It's very possible to have perfectly good mobility, with personal autos being a very secondary mode of transportation, mostly for people with disabilities and specialized situations. The reason most people own cars is that they've been sold a bill of goods -- the feeling that having a car makes you some sort of "upper class" person, and not the kind of riffraff that has to share their mobility with other people. Of course, they do anyway, because they have to sit in traffic, but that's OK, the real upper class people can hop a helicopter or something.