With all the alarms that trigger when a problem arises, even though it might be minor, and all the everyday failures, how does one know which might be a significant indicator of a major problem? Every single one usually has a simple, rational explanation, so not making it an urgent item is a sensible decision. In fact, the maintenance crew simply adds it to a list. Most of the time, this is the correct decision. The one time in a thousand (or even, one time in a million) that the decision is wrong makes it the one they will be blamed for: how could they have missed such obvious signals?