Contractually required. Clients want assurance of continuity of business in case a meteor hits our office or an errant backhoe hits the fiber on our street. We use it for real about one day every 2-2.5yr. It's only enough space for the dozen key people we need to field urgent stuff.

Previously we had clients required us cross train a handful of key employees on their specific stuff so they could acqui-hire those people to maintain their stuff in the event our company went tits up on short notice (we actually saw them exercise that with a prior vendor). They no longer do that as we're much bigger now.