Why cant NEF items be incorperated into the MEL?

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I understand what an MMEL and an individually tailored MEL are but why is there a need for an NEF list as part of an MEL? In other words why is there even such a a thing as an NEF? I understand that an MEL list is minimum equipment deemed safe for flight; however if we didnt have an NEF, a broken table or toilet paper holder etc. would ground us.(So it is kind of all essential in a way) So what says that NEF items cannot be placed on an MEL? If it is because MEL’s are only components and systems where does it say what is and isn’t allowed on them?

Thanks you guys in advance for the insight!