What I see is lot of people want to be the hero with the sword but not have the responsibility. God forbid that you have to do the hard part to be the guy (or girl) that gets top billing. Dark Knights, Paladins (Knights), Samurai, and Warriors all actually existed in history and have influenced fantasy since biblical times. One could say it's a tired trope, I see it as paying homage to the kid in all of us that pretended to wield a sword in the back yard as kids.