The thing is, it's not marketed as a backup service. It's an archive service. If you have business requirements to keep data around for a certain length of time, and things will go very badly (legally speaking) if the data disappears, you might decide to have Amazon store it in Glacier. You likely wouldn't ever access it unless a lawyer or auditor wanted it; if your systems failed, you'd hopefully be restoring from a short-term backup rather than long-term archives.