I have owned a 4 iPhones which I got brand new, with the 5S being the last, that didn't have a lot of scratches. But, after an accident, I had to buy a temporary second hand iPhone 6 and that one had a lot of miniscule scratches all over the screen. So when I got my current iPhone 7 Plus I had a screen protector placed.
Right now I'm on my third screen protector in 6 months.
All I wanna say is, the larger the screen the easier it is to get scratches on it.