So as I said, you have to become a city dweller on your little city island. Fine if you want to live that way, but I don't. I like my freedom to move around and the freedom to live in a place where I enjoy living, thank you very much.
Seriously, the reality of it is this:
Imagine a map where my house is the center. I can draw a circle of approximately 75km radius around my house, and all the places inside the circle can be reached by me within more or less an hour, which I consider my maximum commute time. There are 8 major cities, and several smaller ones within that circle.
Now if I had to rely on other transportation methods than my car, that radius would suddenly narrow down to around 15km (the furthest I would want to go by bike everyday) and well inside that 75km radius, an array of blips of places that are reachable by public transport including just 2 major cities.
Another thing you haven't considered is: what about your social and family life? If you place your job at the center of your life and your answer is to pack up and leave to wherever that is, then chances are you wouldn't be able to see friends and family members very often anymore. In my personal case: my parents are getting a bit older, and I enjoy spending time with them while they're still around so I like to visit them once or twice a week. If I moved to where my job is, and had to rely only on public transport, that simply wouldn't be feasible anymore. Visiting them would become a "travelling event" that would require careful planning and forethought instead of "sure, be there in 30 minutes!". The same deal with spontaneously meeting friends or spontaneous trips to wherever. Right now it's 2 in the morning where I live. If I want, I can be having breakfast in Paris before the sun rises.