You're missing the point
The most common reason for needing a restore, is accidental deletion.
It is, but the most common use for tape is compliance, Many companies, and all public companies have compliance issues,
SarBox, HIPAA, GLB, etc. Most require data retention of many years. In some medical settings as much as 21 years. Do you want to keep that all on spinning disks? or on CHEAP tape sitting in a box at Iron Mountain? In my environment, and that of many large companies, we no longer measure terrabytes, except at the individual database level. We manage several petabytes.
disk based solutions are operationally ideal. Thats why products like Avamar and Data Domain do so well. But for large, long term, low access, storage, tape is still king.