A cooperative is a group of people united voluntarily. A city is not voluntary (yeah, you can move. but it's not always possible or convenient until we have seasteading).
City residence IS voluntary. Very much unlike country citizenship, which, for practical purposes is involuntary for the vast majority of (non-European) people.
What do you mean? Country citizenship is not voluntary for EU citizens either. Did you mean country residence?
In practical terms, citizenship does not restrict residency in Europe for Europeans.
Almost every legal adult who lives in a city chose to live there. Yeah, choices have practical constraints, and yeah, it can be difficult to change once you've committed. But that's true of almost any complex product available on the free market (CRM systems, a university education, database software, operating system software, etc.).