Nail on head.oh god. i don't do this, but the friends i queue lfr with sometimes do. and the reason they do it is because it is a harmless action to need on a green, but they know that there are those who will take this as a serious offense and bitch about it.
it's intentional shit stirring, but i look at it as more of a commentary on how uptight the WoW community has gotten. people feel like superior players for greeding on items like they're "supposed to", but the need option is there (for those who can use it), so there really is no harm in using it.