In D&Dese, making an object float through the air is a spell-like ability. In this case: mage hand.
Physical objects don't hurt ghosts, magic does. Ghosts are no longer scary when you can just whack them with the candelabra that you were nervously skulking through your dark house with.
Fire elementals could have some sort of body beneath the flame. See Skyrim: fire atronachs. Kill one of these, and they leave a sort of rusted iron-looking husk behind. If you're fighting something that's pure flame, poking it with a stick doesn't make much sense.