One thing thought. We need to dispose of corpses in a way that they can fertilise the crops. Otherwise, in a not so far future, many people will die.
Some people choose to be buried in cardboard coffins for that very purpose, so they can naturally rot and fertilise the earth, perhaps the world would indeed be better off if more people chose that option.
Also, a relationship is between people, not bodies. I like to think I love people, not their bodies. Harming the body harms the person, when it's alive, but harming the corpse does nothing.
Again this is a cold logical way of looking at it. But the thing is, after experiencing the death of a loved one the majority of people tend to be overcome with emotion. Religion obviously plays a bit part in respecting the corpse, but even non-religious people will tend to treat the corpse well.
No matter what people need closure, the attachment and memory we have of a person does not go away after they die and we tend to transfer these things to their body even though its logically just a cold slab of meat.
People who can detach themselves from all emotion when a loved one dies would either be classed as in denial or completely sociopathic.