The disks for Glacier cost $0 because you already have them.
Last I was aware flash/nvme storage didnt have quite the same problem, due to orers of magnitude improved access times and parallelism. But you can combine the two in a kind of distributed reimplementation of access tiering (behind a single consistent API or block interface).
But then what do you do with the other half of the disk? If you access it when the machine isn’t dormant you lose most of these benefits.
For deep storage you have two problems. Time to access the files, and resources to locate the files. In a distributed file store there’s the potential for chatty access or large memory footprints for directory structures. You might need an elaborate system to locate file 54325 if you’re doing some consistent hashing thing, but the customer has no clue what 54325 is. They want the birthday party video. So they still need a directory structure even if you can avoid it.