Have you ever made a purchase and then realized you didn't get what you wanted out of the transaction? You might look back at the listing and realize, "Gee, I missed that" or "I must not have read this clearly." In your defense, companies often keep details thin intentionally and don't always put all the specifics up front or in big bold letters. I'm not making any accusations of dishonesty, but it seems to have always been the nature of the sales pitch since the dawn of humanity. If a business can present a product in a more favorable light (aka minimizing what it lacks), it might get the traction they're seeking monetarily. Believe it or not, the same goes for digital goods, including movies.
