The snippet allows to get notifications when a minute number changes on a clock. So if you have a clock displayed in your app, but don't have seconds displayed, you don't need to maintain 1s interval timer. Just subscribe to event and unsubscribe when not needed.
Application suspending is handled additionnaly, because it makes timers stop. That's why when app is resumed, a Delayed
clock tick event will happen.
Of course, there can be a second-based event, if needed. The service will still be useful, because it performs timer management.