When the DM describes zombies, skeletons or any other undead that attacks the party, how often does he mention what race the creature was in life? How often do you even think to ask?
As a player when I hear “skeleton” I always assume it’s a Human skeleton. I never ask if it was originally any other race. The same goes for zombies, mummies, and ghouls. I always just assume that it was human and now it’s undead. Even the description in the Monster Manual and online compendium just classifies these monsters as medium undead. But in a fantasy setting there’s no reason to assume that every undead you face was once Human. With so many other races represented in the world why wouldn’t some undead creatures have once been a race other than Human?
This might seem like a really small detail, but it can really change the way an encounter plays out. Not to mention it can drastically change the mood of the encounter. Think about it, how much more terrifying would a skeletal army be if they were once Minotaurs? What about a zombie horde full of animated Dragonborn corpses? What about Halfling mummies? Or Pixie ghouls? It only takes the DM a few minutes to identify what race the creature was before it became undead yet it can drastically alter how the players perceive the encounter. Where they might rush haphazardly into a group of “normal” skeletons, they may now rethink their tactic once they realize that these undead are special.