Agreed on this one. Which was a bit fun at first- walking into a store and seeing one you didn't even know existed. But then they took that to another level with the Funko Store exclusives, so they'd either show something on the back of the box that the average Joe wouldn't know was only available on Funko's site and they'd never find it, or they wouldn't put it on the back of the box, and it would sit and rot on Funko's site because nobody knew it was there other than the super hardcore fans. With a lot of releases nowadays, they don't even show the other figures on the back of the box.
Having some sort of retro cross-sell type on the back of the box showing not only all the other figures, but where to get them, would be best. They already do that when they reveal product online- show the logo of wherever it's exclusive to, so doing so on the packaging would only make sense. Not everyone is chronically online, or follows Funko-related pages.