I think it's important to a community for it's citizens to have good citizenship because of the many benefits it brings.
If people have good citizenship, their community could be a cleaner, safer, prettier, and happier place. If people are caring and are willing to take the time to help others, they will not just be turning their city into a better place, but turning into better, happier people themselves.
The people in that community will not be as selfish, demanding, or even stressed as people who don't show good citizenship. If they are constantly outwardly focused, they won't have any time to be stressed about their own problems. They also won't have as much stress based upon time, like being late. It won't matter as much if they are late because others will help them out with their work.
If you don't show good citizenship, you won't have any of the moral and citywide benefits I just described. There could be more crime in your city because people are meaner people, you could be overall more stressed about the future, and there wouldn't be as strong of a sense of community in your city.
Any community would be a safer place if it's citizens showed good citizenship.
I hope this helps you