Villains don't need to be tragic or misunderstood. They need to be ENTERTAINING.
Giving villains a sad backstory can sometimes feel like justifying their actions for some cheap sympathy. "Oh no, he was orphaned as a baby, he was picked on as a child, his parents never loved him, his wife left him and took the kids, he actually has good intentions but is horribly misguided, I know he's about to kill the hero/destroy the city/blow up the world but I can't help but feel sorry for him."
People can do bad things not because of some motivation or agenda, but because they're just jerks.