Not all poisonings occur because of assassination attempts. (in fact I imagine it to be a very tiny minority of poisoning cases) Someone can be poisoned by picking the wrong mushroom, thinking it to be a different edible one, or by eating the delicious looking tide pods or by drinking a cup of the methanol-rich alcoholic beverage your friend made (or by drinking too much alcohol in general).
Not all poisonings occur because of assassination attempts. (in fact I imagine it to be a very tiny minority of poisoning cases) Someone can be poisoned by picking the wrong mushroom, thinking it to be a different edible one, or by eating the delicious looking tide pods or by drinking a cup of the methanol-rich alcoholic beverage your friend made (or by drinking too much alcohol in general).