The minimum standard of good behavior need not be explicitly stated, and violations can be dealt with as they arise. The problem with written sets of rules is that they can be subverted and misused.
That's also a problem with unwritten sets of rules that are based on vibes. If the baseline expectations are written down, at least people can notice if the rules aren't being followed.
Plus unwritten rules can be subverted and misused at least as much as written ones.
Humans are always gonna do human things.