Storing it encrypted also means you have to ask what happens if the key is leaked — for example, if I tried to sell movies that way rightsholders would be unlikely to accept a system where you could pay $10 and then give the decryption key to all of your friends, leaving me no way to revoke it.

For updates, you can definitely replace things but that's expensive if you have to pay a transaction fee regularly and it could quickly get to non-trivial storage sizes if you have to store obsolete versions in perpetuity, especially with non-trivial metadata overhead.