If there's someone who is not using a screen protector and do not have any scratch on the phone, then he / she should be considered extremely lucky, or they can't see scratches!
Gorilla Glass, Dracula Glass, Dragon Glass, they all scratch, overtime. I didn't use any screen protector on my S4, as I was confident nothing will happen, then after four months of usage I saw 3 light, very light scratches, that's it, applied one without hesitating an instant. Some scratches are not visible under normal light, just put your phone under a LED / CFL, then you'll see magic
So in short, yes, screen protector is a must, regardless of whatever fancy named glass your phone has.