By the owner having the short-sightedness to not have a queen size.
That is true and defies the laws of physics.
cats just love to live large
They spread out to make themselves as big as possible...the last one I had stole the warm spot on my side of the bed when I'd get up to use the bathroom, and she wouldn't budge when I came back...I'd have to sleep near the edge of the bed...I sure miss that little cat.
My cat does that!