It's triage. Usually you'll want to get back to the details and address them at some point. But given finite resources, it's a waste of time to try to dig through details when more pressing issues need attention.
You can always delegate the "details", but there's a difference between delegating and deferring (the work for yourself). Knowing what to delegate is very important, of course, which is the main point of edw519's comment, I think.