The seller owns the license, and they run out. They sell you the ability to view content for which they have a license. At some point they will not sell anything but only offer a subscription to their service app and one can view anything in their catalogue for a monthly fee until licenses change hands. This is why services promote those movies and TV shows that are "Leaving Soon." I'm not saying it's not f#%ked up, but it is funny that many will spend big sums at the movies for one viewing and have no issue while others will complain about a digital purchase made years ago and watched more times than they can count being taken away. Move on with your lives and buy physical copies when you can do so.