See what you are saying
The commercialization of it though
Survival situations.. what can you do.. not even Cain and Abel but if someone dies first and the agreements made.. few stories about that, the. Other side of spectrum warfare(feeding humans to pigs, selling bacon to humans.. evil curse bad diet stuff), then also if leading armies around especially before mass troop movements with fuel but eating the enemy can sustain an army.. maybe the soldiers do or do not know. They tell us that one in plenty of shows and movies. Like Game of Thrones comes to mind