I find these discussions seem to be dominated by young urbanites. People who don't need a car to get around as opposed to the huge number of people who live in areas that require a car to function. They are also physically able to bike many miles every day in any weather.

I took public transportation when I lived in a big city and was glad to have it but anytime I needed to go beyond a limited area in the city I needed a car. Now I live in an area with very limited public transportation and very very little is in walking distance and biking for my needs is not an alternative. Frequently using 100% public transportation routes would increase your travel time by a large amount, time you may not have or want to sacrifice. If you live in country like France it seems like the transit unions have a stranglehold on the nation as they can shut down everyone at will, if you have a car you at least have an alternative. There are also breakdown issues, maintenance shutdowns, etc. You also run into the last mile issue a lot. Where you need to go is frequently not a reasonable distance from the stop. I usually needed a car to get to the train stations for instance.