I believe this is like everything else in life.  The safer you feel, the less careful you are.  If you put a case on you will be less careful, and therefore, more likely to drop the phone.  If you drop the phone, even with a case, there is a chance of breaking the screen.   I choose to enjoy my phone as is and be careful.  I am unconcerned about a little wabi sabi from everyday use, but so far the phone remains pristine.