I can speak to part of the rationality around Snowball:
The old method of customers sending in hard disks and AWS importing them turned out to be _incredibly_ high touch.
* Customers would put the wrong labels on the wrong drives. Given they were encrypted, and the label details were critical to matching the right disk with the right encryption key, that was a big issue.
* Imports would routinely fail due to all sorts of driver bugs both on the AWS side, and on the customer side. The number of fringe NTFS quirks was phenomenal, let alone all the wide range of other formats that had to be handled
* Encryption tooling still really isn't all that user friendly. Too many opportunities for mistakes.
* Drives would get damaged during shipping.
* Stuff would go missing in shipping.
It just didn't scale as a solution, and caused unending customer pain and frustration.
Snowball solves _all_ of that, by taking out of the equation almost anything about the process that customers could get wrong. It handles all of the encryption stuff, is extremely ruggedised, has basic tracking. The label is an e-ink display that automatically contains all the right information. It becomes a "just works" solution.