However, not all backups are continuous and pervasive. There are often backup windows, gaps, and processes that halt with no one noticing. Ryuk also actively disables and deletes backups to maximize impact, while also seeking out mount points that might be backup targets - and encrypts those as well.
Of course, we're also talking about hospitals here. Even a well-managed system with hourly differential backups leaves plenty of time for radiology data to be lost in the critical hour before life saving surgery.
More realistically though, how long would it take you to discover and remove a sophisticated penetration, then restore every device, ensure none of the restores are also infected by the malware that had probably been there for a while, and bring a hospital system with thousands of impacted systems back online? 72 hours? A week? A month?
What happens to the patients? Admissions to the emergency room? What if adjacent hospitals are also hit, or are already impacted by the COVID spike and have no open beds?
People literally die due to hospital ransomware attacks. No one deserves that.
Ransomware is akin to kidnapping, it's just the data and customers that are held hostage, not kids or loved ones. Always blame the criminal, never the victim.