Hospitals understand the need for mattresses to be adjustable. All things considered, patients have to be treated throughout these hostipal wards for all types of things. It can be some manner of trauma, such as an injury or something of that nature, or it can be recovery from a surgery. Sometimes its just a matter of keeping the patient as comfortable as possible.
The point being that sleeping on your backside, flat and out, is oftentimes not necessarily the greatest thing available for you. Adjustable beds are the remedy in such cases.