Redundancy -- you don't need to keep backups of a blockchain but you do if everything is centralized in a single place.

It depends on the value of the backups I guess and the total cost involved. If you're looking at store of value there needs to be backups of backups. I see room for both depending on the needs of the business. It's just a trade off -- the blockchain is inherently more stable and secure than a server for certain purposes and server is far faster and cheaper depending on how you use it.