On some cars (like mine) the brake disk sort of "free-floats" on the hub when the wheel is unbolted. If the disk is skewed, then some ham-fisted monkey with his impact wrench set on "annihilate" reefs the lug nuts down, especially if he doesn't follow the correct sequence, it can put uneven stress on the disk.
I've seen some guys put the lugs down snug and then hold the trigger until they won't move any more. I had to put a 3-foot piece of pipe on a tire iron to get them loose so I could re-torque them correctly because they were going NOWHERE with my X-wrench.