In many cases, appeals to authority are a subset of association fallacy (which surprisingly hasn't been noded yet). If a celebrity is loved, one might try to get some of their positive reputation to rub off on the endorsements they make. If a leader is respected, one might try get some of that respect to rub off on to statements they've made. If we take 999 statements from any source and can prove they are all true, it would still be a fallacy to assume the next statement will automatically be true.
One might expect appeals to authority to be more common in authoritarian societies. It must be right because X says it's right. If an authoritarian society regularly relies on appeals to authority in order to justify their policies, then the population becomes conditioned to seeing and using appeals to authority in discussion and debate. Attaching a famous name to a quotation then makes that quotation more credible than attaching a less famous name to the quotation. As a result, it may be possible to measure how authoritarian a society is, by measuring how often appeals to authority are used by the people in that society.