It then becomes annoying for everybody: As a driver, you will be stuck in traffic and pollution most of the time. As a pedestrian, you will have to always mind your surrounding to be safe and you will have to smell the horrible car exhaust.
Since our center is mostly car free, it honestly feel more convenient. Sure you have to sacrifice the convenience of being close to your car, but you can be in and out of the center in a matter of minutes, never be stuck in traffic, and being there is much more enjoyable.
Also, my city converted a lot of road into pedestrian way and they added a lot of place to sit down, take a break, ... Before that, you where always stuck in a narrow sidewalk, bumping into other people with cars going full speed less than 1,50 meters next to you... Not really a pleasant experience. Your only hope to catch a break was in the shops themselves, meaning you where trying you damnest to go from shop A to shop B as quickly as possible. It made people overall more aggressive and your experience very bad.
And finally, they added more green space which help prevent flood which started to appear in the last years because we had too many area covered in asphalt.