If the purpose of a hospital is to only cure enough patients, the question becomes; "Why is the purpose of a hospital to cure just enough patients?"

You aren't supposed to just use it to argue in a circle. The purpose of a system is what it does, so, why is that the purpose of the system and why do we have that system?

It implies that the system is working as intented, and that's why we need to destroy it to build an entirely different system.