If your alarms always go out when something is wrong, you do not need a graph. However, alarms are never perfect. Issues can occur without triggering alarms at

If your alarms always go out when something is wrong, you do not need a graph. However, alarms are never perfect. Issues can occur without triggering alarms at all. The graphs cover your blind spots; they help you debug the issues that you do not yet have reliable alarms for. If an issue occurs without triggering an alarm, but the graphs help you debug the issue, then you should create an alarm that would have caught the issue. Next time, you will get the alarm, and will have a better idea of what is happening without having to look at the graphs.