Maybe eventually you can legally BUY a movie from Amazon.
(And NO, you cannot buy a movie today, no matter what Amazon calls it. Their "purchase" option is just a long term rental until Amazon, or the actual copyright owner decides to withdraw your ownership from you. Like in one case of a Disney movie some time back where "owners" of that movie had it taken away because Disney had some other exclusive streaming offer they were making to others.)
All that said, ten years ago it would have seemed unthinkable that you could download and "own" an mp3. But you can. I've done it multiple times from Amazon. I can buy tracks or an album. Download. Put it on all of my own personal devices. In every sense I feel like I made an actual purchase and received something in return. Like any purchase it's my duty to take care of it (eg, make sure I have reliable backups, etc).
I think the book and movie rights holders are taking longer to come around to giving true DRM free ownership. But I think it is inevitable that they will. Or maybe they won't, since they already have effective DRM tragedies / strategies in place. Unlike mp3 which did not. And mp3 players which did not and already had massive market penetration.
Still I can rip DVDs and play them on my own personal devices. I can watch a movie on a plane. Etc.