Why is creating undead Evil?

[MaxiDuRaritry]

I like that explanation.

There's also the fact that undead are almost universally evil themselves, so by raising zombies and skeletons you're bringing evil into the world quite directly. Sure, they're under your control, but you're basically gambling the safety of any innocents nearby that you won't lose control. And while you may accomplish enough good to outweigh that risk, this is D&D: you could have literally taken the same experience and effort you spent learning to raise the dead and learned something else about as effective, so choosing necromancy is, at best, a little bit selfish and reckless. (With a caveat that this only applies under most circumstances; there are always exceptions.)

Zombies and skeletons are entirely unintelligent and thus cannot have morality, unless they're animated by [Evil] energies, which negative energy is not. And neither of them have any kind of motivation at all, not even instinctual ones, and they literally stand there and do nothing until the once-living bits they're composed of turn to dust unless commanded to do something in particular.