Why is creating undead Evil?

[OGDojo]

Iirc creating undead adds negative energy to the world and disrupts the balance, so is universally evil, even if you use them for good, as the Greater Good demands you never make them. Don't have a source for that, but I do know that having undead and negative energy around empowers Attropus from Elder Evils and moves us closer to the apocalypse, so that's also a thing.

perhaps you can use this as an option to bring an elder evil into the world. storywise it would be like "the world has legalized Necromancy and corpse labor to help with tasks like mining and handling hazardous things. but in turn more Negative energy is being released and waking up Attropusm the elder evil and no one knows until he busts through the earth or descends from the clouds or rides in on a giant hippo (however he comes in) and begins WRECKING the world and causing chaos. it then falls to the adventurers to fight him off.