"We have backups" is an assumption, not a plan.
Most organizations have backups running somewhere. Far fewer can say how long a full restore actually takes, which systems come back in what order, or when the process was last tested against a real failure rather than a green status light.
Disaster recovery is the decision about how much of that uncertainty leadership is willing to carry - and what it will fund to remove. It starts from two business answers, not a product: how long the organization can operate while a system is down, and how much recent work it can afford to lose.
Those two numbers set the budget. A recovery target of minutes and a recovery target of two days call for completely different investments, and pretending both are covered by the same nightly backup is where most plans quietly fail.