Animation Controllers instead of Humanoids. Any downsides?

I used to add a humanoid to my rigged animal models to make them animatable.
But yesterday I was told that humanoids cause a ton of unnecessary lag and I should simply add animation controllers instead.

So…Why do people even use humanoids for animals and other non player objects/characters in the first place?
I’ve seen a lot of people do it that way in tutorials.
Is there any downside to simply adding AnimationControllers instead?