Why is there so much misconception about Retin-A (tretinoin)?

I'm puzzled that so many people think that Retin-A is just a fancy name for vitamin A all wrapped up in expensive packaging. Retin-A is indeed RELATED to vitamin A, but it is an acid derivative of the vitamin, retinoic acid. Retinol, which IS just a fancy vitamin A in a cream is something entirely different. And ingesting vitamin A through diet has absolutely no benefits that Retin-A imparts on the skin, as a)it's unrelated and b)it's not topically applied, therefore it can't have the same effect whatsoever. Can someone explain why this is such a misunderstood concept? Anyone?