Look: You, me, and the rest of our nerd battalion see this as one big travesty and mockery of the sacred text that PJ has tainted with his Hollywood yadda yadda. But to John Q. Public, who's never read the books, never played D&D, and doesn't know the diff between a Dunedain and a Nazgul, the Legolas/Gimli dynamic played out in the films is simply the sword-n-sorcery equivalent of the classic "straight man" routine. Given that the characters don't have a lot to do dramatically-speaking in the films besides have Aragorn's back, and the whole trilogy can get a little dreary what with all the "The quest shall claim his life" and "Here you will dwell bound to your grief..." doomsaying, I'm sure PJ felt a little levity was in order.