It's more of a case of the dvd seller offering a service where they will almost but not quite always replace scratched dvds with new ones free off charge and people becoming reliant on that.
The DVD seller isn't making the copy, but requesting them from the original manufacturer. The DVD seller telling the purchaser that this service is contingent on the manufacturer providing back up copies free of charge. However, the manufacturer can at any time refuse, if they no longer make them, or no longer wish to support it.
Its probably not Apple's decision to limit the download, it most likely the original rights holder.
