Because they make more money on licensing than selling the digital copies. Companies that offer a purchase option, like Amazon, usually only sell you the right to access the media through their platform and offer no way to take it out.

Now as time has shown us they can take that away as well as you don’t actually own the digital content you purchased. For example Sony pulled titles that people bought and thought they owned from their store and offered no way to download the content.

It’s just more bullshit and corporate greed. Part of why companies aren’t selling physical media anymore is because if you can’t own something they can keep charging you for access to that thing and infinitely double dip.

NYT Lifehacker