That's a choice that companies make. I've certainly worked at places which don't test DR, while at my current job we do annual DR runs, where we'll bring up a complete production ready environment from scratch to prove that the backups work, and the runbook for doing a restore actually works.
I'm retired now, but the last place I worked estimated it would take months to do a full restore from off site backups, assuming that the data center and hardware were intact. If the data center was destroyed... Longer.
