I think the answer is buried somewhere in the mists of...time. Put another way, there is a temporal degree of respect for the dead, i.e. can you and for how long put the wishes of the dead above those of the living.
Of course, for immediate death, as others have noted, there are plenty of "stakeholders", family members, etc. who have direct interest in the wishes of the dead being upheld (not having their communications exposed, as others have noted). These needs must be considered, but eventually those grandchildren will also themselves pass, and those stakes will have also vanished.
Even for immediate death, the wishes of the dead can be invalid and ir-respected, such as in the case of a suicide bomber or a recently deceased captor/dictator.
On the flip side, for those dead (tens of) thousands of years, we engage in a practice known as archeology, that I think you would have a hard time arguing the opposite - the information we glean from their table scraps is too valuable to worry about their death wishes, assuming they had any.
In the great in-between, then, the question is, whose wishes matter more? Those of the deceased or those of the living. Usually, those of the living. And it is generally in our interest that we not disturb the dead too much, because at least we would like to live in a society that continues to grow, and does not need to disturb them (too much), respect our own wishes, etc. But ultimately, once it can be said it no longer harms any living, or any future living, then the desires of the living trump the desires of the deceased.
Of course, for immediate death, as others have noted, there are plenty of "stakeholders", family members, etc. who have direct interest in the wishes of the dead being upheld (not having their communications exposed, as others have noted). These needs must be considered, but eventually those grandchildren will also themselves pass, and those stakes will have also vanished.
Even for immediate death, the wishes of the dead can be invalid and ir-respected, such as in the case of a suicide bomber or a recently deceased captor/dictator.
On the flip side, for those dead (tens of) thousands of years, we engage in a practice known as archeology, that I think you would have a hard time arguing the opposite - the information we glean from their table scraps is too valuable to worry about their death wishes, assuming they had any.
In the great in-between, then, the question is, whose wishes matter more? Those of the deceased or those of the living. Usually, those of the living. And it is generally in our interest that we not disturb the dead too much, because at least we would like to live in a society that continues to grow, and does not need to disturb them (too much), respect our own wishes, etc. But ultimately, once it can be said it no longer harms any living, or any future living, then the desires of the living trump the desires of the deceased.