Why: I'm having a hard time seeing why this ever matters.
Why: The ability to restore 30% of your HP right after getting pounded on earlier can make that character liable to be able to fight immediately, then be restored if necessary. No guessing, no luck, HP based, so at the most you can heal 24HP. For some areas, that's just enough to keep your units chugging away.
There is no greater challenge than beating the limits you set on yourself.