I was talking to some ethologists in a special interest group. Several of them agreed that practices like this were actually good. There was one animal psychologist specializing in raising domesticated rabbits and she said that she was doing a study in which it was shown that the companions of a rabbit that died lived longer if she kept the rabbit that had died in the cage for a few hours instead of immediately taking it away.
It's possible that we have some sort of genetic program that separates out our emotional responses and anticipation between a social peer that has disappeared mysteriously and may have come back or may have been a victim of a predator, high stress situation, and a peer that has died of natural causes and now can be forgotten, still stressful but probably less stressful.