the ranges are determined based on a standard players shoving range
for instance your given A A, K K, or Q Q, your not really going to shove cus you want value most of the time, so if somebody shoves they most likely have something less then this or a drawing hand.
on the other side of the coin you have shoving ranges for yourself
you can shove with a pair of 8s because an opponent in theory needs better to call your shove (dependant on stack sizes) you can win by all opponents folding which would be a nice increase in likes of MTTs and STTs, or you can win by showdown, in most instance if somebody calls they usually have a hand like A K - A J, bad players even less then this, and therefore it becomes +EV cus you win chips when they dont call, and half the time when they do call.
if your shoving A A aswell they cant take that out of your arsenal so when you shove they in theory need a really strong hand to call your shoves