wearing necklaces that have verses from the Quran on them a sin?

I don't understand how this is a form of Shirk? I'm not Questioning Allah but no body has given me anything from the Quran that says we cannot wear necklaces with Quranic verses in them can somebody please explain how this would be shirk??? I mean it is Allahs words in the necklace to begin with? Please don't be rude in your answers I'm genuinely unsure about this and would like to know more about this topic