I wish every body was the same, but unfortunately, it's not. It's the same reason or lack of reason perhaps, that one person is deadly allergic to peanuts while you or I have no reaction to it, or pretty much any other medical conditions that some have and most don't. It's really a luck of the draw. For example, my dad constantly licks his lips and snores / mouth breathes during night, and yet he has normal lips, and I am guessing I pretty much did the same when I was young and well... here I am.