minhag - Why do we cover the challot on Shabbos?

The answer I learned growing up was that "we don't want to embarrass the bread because we are first making kiddush" or some variation thereof. I later learned that is a zecher for the ma'n which fell with a coating on top and bottom. Where does that first answer come from? And, if it is a legitimate source, what does it really mean (ie bread doesn't have feelings!)?