When you "buy" digital content, be it music, movies, software or games, you almost never actually buy the product. What you get is a limited license to view or use the product for an undefined amount of time.

Generally, companies reserve the right to, at any moment, restrict how can access the content (e.g. force you to use a specific device and/or program) or remove your ability to use or view the product entirely.

For example, a movie or song you've "bought" might get removed from whatever streaming service you're using. A game or program might stop working due to changes in the DRM system.

Actual example from less than half a year ago: Autodesk disabled people's supposedly perpetual licenses for Autocad and other software, forcing anyone wishing to continue to use their software into a subscription.

Imagine buying a house, only for the seller to show up 10 later and state that they change their might and staring from this point in time the house is no longer yours - despite the fact that you've paid for it in full - and you own them rent, if you want to keep living in it.