We all know that for blue and above there's no point - you might as well collect them at the post office later. But for green (just for the armor/weapon parts) there's a tendency to try and grab them in case you forget to come back and collect it later. Silly I know. Death isn't worth a green! At the other end of the scale there's yellows from ToC's - there's something inside all of us which says "must go and grab it" because we somehow don't trust it to be delivered to the post office and it's too valuable to lose!