Funerals are for the living, not the dead. I struggle to think of a good reason not to acquiesce to their wishes prior to dying, so as to make their grieving easier, given that yours will not matter at all then.

Sure, that makes sense, but not everybody leaves a will behind or lets anybody know about their wishes when they die, out of ignorance, sudden death, there are a lot of reasons why you may die and haven't told anyone what to do. Happens a lot with organ donors, for example.

In lieu of the deceased's will, the relatives need to make a decision. And, IMHO, this whole cannibalism thing is a lot harder to wrap your head around than having your loved one's organs harvested to save somebody else's life, for example.