I get that people worried that the ancestors would be ticked and try to punish you for that, but wouldn’t someone…wouldn’t lots of someones have tried it over many centuries and places, and wouldn’t those tribes have more food, more weapons, more trade goods than their neighbors? We think of it as a waste because we don’t believe the ancestors are really going to punish you for that. We have slight vestiges of that in our language. “My father would come back and haunt me if I gave that to his brother’s wife.” “Miss Foley would turn over in her grave if they switched back to that history text.”
Look at these these things in the broader context of sympathetic magic rather than strict appeasement of hostile spirits. If I act in generosity, the gods are do not merely like me better and consider being generous to me also, they are bound to do this, because that is the nature of the universe. If I give, I make the universe give to me as well. As far as grave goods go, the items are not gifts, they are not objects that the deceased owned, they are items which have the spirit of their owner in them. Especially with items associated with magic, such as metalworking or musical instruments, they would be regarded as something it would be wrong for another person to use, or might not work successfully.
Do we regard that as impossible and unnecessary? The exhibition of the piano John Lennon used writing “Imagine” was booked solid, and people wept to touch it. We have a strong Germanic and Celtic tradition of swords that can only be wielded by kings. In more abstract but only slightly less mechanistic terms, religions offer the same deal: in Buddhism and even Confucianism, acting in accord with the true nature of how the universe is supposed to work means that the universe will help you; in Hinduism, the actions of karma add to your store of what the future will bring you – the wheel may turn slowly and you cannot force the hand of the universe, but a long justice will prevail. The early Hasidic rabbis believed they could make the messiah come with their mystic practice, their recitation of letters and words.
There are more than threads of it in Christianity, and those are the hardest parts for us to understand. Bread cast upon the waters returns a hundredfold. Is that a law, or a tendency? Either way, it is an indication that generosity begets generosity, not just from the people around you in a mid 60s sense, but from the world itself. The early church collected relics of anything that Jesus or one of the apostles may have touched (and there is NT support for this around a bit of cloth), believing that they might heal. The more complete teaching, of God being generous by his own choice because that is His nature, supersedes but does not discard the earlier, perhaps more primitive one. We are judged in the measure that we judge. We are forgiven in line with how well we forgive. In neither case does God refuse to be merciful when we do not deserve it, but there is a strong sense that we must somehow go along with this to get there. It is not a present we receive that God might withhold until we give something ourselves, it is a road we must travel to get somewhere. I admit that God does phrase it in the former way sometimes, and does not draw back from framing it as an exchange, an almost mechanistic practice. There is a deep truth that we must act in accordance with His nature to know Him, much closer to the eastern ideas of adjusting ourselves to the fitness of things, and the pagan ideas of making the gods provide fertility for the tribe by bringing plants and animals for sacrifice, than it is to our rather chilly and abstract notions of careful requests to God of how we think the world should be run.