This is my experience, having lived most of my life in small places (ranging from a monastery to a city with 25k people) while listening to people in big cities complain about their commutes.
Now I live in a city that isn't exactly small but not huge either. I'm already suffering the consequences of traffic and longer distances. Moving out of small cities is when I started to actually need a car... of course having more people and congestion doesn't show up in traffic only; it's also in the grocery store queues, restaurants packed full, parcels not delivered to home because they're too busy to deal with everyone personally, etc.
The thing with smaller places is that you can generally get like 80% of what you need locally, but on occasion you have to go a few towns over or into the nearest city to get that 20%. So you can easily live in a city w/o a car, but it's substantially harder to do so in smaller places.
Also, my experience is that the 20% is more like 1-2% (when I lived in smaller cities, I needed to visit other towns or bigger cities a few times a year).
Like I said, I started needing my car only after I moved out. As a matter of fact, I only got a car a year before moving out, and I only got it because it was given to me for free.