The body is what binds them to this earthly life. When you die, what makes a person (or a cat) a person - the spirit, soul, whatever you want to call it - no longer resides in the body. The body becomes an empty vessel and is no longer, imo, part of that person. I recall going to see my father in hospital shortly after he'd died. What struck me was that there was just no-one there anymore. He didn't look like he was asleep, he looked as though he had left his body.