Why did Herodotus think that different societies considered their own customs best?

The Greek historian Herodotus observed that different societies possess distinct customs and that individuals naturally perceive their own society’s traditions as superior to all others.12

He illustrated this perspective by recounting an experiment conducted by the Persian king Darius I. Darius asked a group of Greeks how much he would have to pay them to eat the bodies of their deceased fathers, which they refused to do at any price. Conversely, he asked a group of Indians who practiced ritual funerary cannibalism what would induce them to burn their fathers' bodies, a suggestion they found deeply abhorrent.2

From these observations, Herodotus concluded that each nation considers its own customs to be the best. In the context of ethical relativism, this suggests that moral standards are social products that vary by culture, and there is no culture-neutral standard available to objectively judge one society's customs as superior to another's.12