What is the distinction between "'private' videos" which are presumably created by individuals, and privately owned media (like movies) which are created by corporations?
I'm using my own examples here, one of the projects I'm apart of distributes personal videos over HTML5. Having these just stored on a file system is vulnerable in a way that a sysadmin could view the video or if the file system is compromised [the exploit could reveal the video]. Those are what I could think of off the top of my head.
Having the video encrypted (since Netflix is pushing for it anyways, why not use it to my benefit), allows me to provide the keys directly to the content owner for decryption.