Mainly because its citizenry and its bureaucracy have a personal attachment to their city and society being run cleanly and efficiently. This is not the case in cities like Paris or NYC, where most people see themselves as guests or even victims attempting to finesse the system by doing the least work possible. Since pretty much every public worker abides by this system there is an implicit agreement to never pursue any offenders (be they lazy or just incompetent), for everyone is used to doing the bare minimum and they like the arrangement.