This is really nothing new. Back before there was such a thing as prime video, Amazon offered just videos you could purchase. Some of these were videos that weren't available anywhere else (and some still aren't.) I did purchase one knowing full well that it could get removed, so I used some tools to rip the video into a format I could keep. Sure enough, a few years later the video was gone. If I hadn't make a backup for myself, I wouldn't have any recourse.