In nearly every game with melee, such as Halo, Gears of War, even the Battlefield series, it's often a stupid tactic that is either cowardly, nooby, or just plain irritating and lame. You have a gun, use it.
I'm a ranged man through and through and make use of every gun from snipers to pistols. I despise dorks who rush my position intent on using their machine gun more like a club than a gun. I love pumping said meleers full of lead when they try to cross the no man's land, however.