This phrase is stupid and it gets repeated so much. It's pure vapid mangement consultant dreck. Imagine I told you that my car was running kind of hot and I needed to replace old coolant to make the system work better. If you told me 'ThE PuRpOsE oF a SyStEm Is WhAt It DoEs' I would think you were missing some braincells.
Sometimes the purpose of a system is what it's supposed to do and it needs some small maintenance to make it work right.