Why does the service restart when the Activity is closed?

Question

Java

Good afternoon.
I observe an interesting picture: I have a service that works in the background. Runs once and works there without completion (essentially listens to Firebase and saves to SharedPrefs if there is a change). Now, if the Activity is terminated, the running service is restarted for some reason (onStartCommand() fires). Of course, while this does not create problems, but in my opinion this is not a very good practice. How to be in this situation? Thanks in advance.