The dead body has value because the human person does. How we treat our dead reflects our views on what we think about the living.
The assisted-suicide movement boosts suicide in many forms. One of the most insidious is known in euthanasia parlance as VSED.
In my experience — as a once-practicing trial attorney — when the smell of money is in the water, ideology is generally not the first priority.
Maybe there is no evolutionary explanation. There is certainly no discernible natural-selection benefit.
The “Ocean rights” approach would make the creatures of the sea co-equal with humans.