Indeed... In all the years I've had mobiles (20+) I've only ever broken one screen... And that was when it fell out of my pocket and got run over by a Land Rover! Even then the glass (being old fashioned, non super hard - and brittle - glass) didn't break, but it obviously flexed enough to kill the LCD panel underneath.
My current phone (a Nexus 4) is 18 months old, used daily, has no screen (or rear glass) protector, just the standard optional bumper case (which has saved it from a couple of drops), and do you know what? When you take the bumper case off, and give it a polish, it looks new.
Because I don't throw is in a pocket with all my keys and small change, or a handbag full of what is best described as "life-gravel"! It lives in a pocket, on its own, as have all my mobiles.
Treat your phone like the essential (and valuable) piece of kit that it is, and it will last.
Kick it about like a football, or sandblast it with coins and keys and it won't.