You have a defective unit if that happens. The screen is made with gorilla glass. Four years, every iPhone, no screen protector, no scratches.
So you are saying the hundreds if not thousands of people that have scratched or damaged screens have purchased defective units?
I've seen all ranges of iPhones, even the new 5, get scratched by simplistic things such as dust constantly rubbing creating friction inside a leather pouch. The friction causes the scratches, not one or two scrapes across but many consecutive swipes. Same with many hits from keys in a pocket. The constant force strains the integrity of the screen.
It sounds to me that you have drank the kool-aid from the marketing campaigns. Gorilla Glass, which is actually just a named brand Corning made up for its glass is strong yes, but not unbreakable.
Not to mention that it is really a mystery as to what glass is used in the iPhone leading up to the 5. No one truly knows but this article seems to make it pretty clear that Apple had not been using Gorilla Glass until recently (
http://9to5mac.com/2012/03/02/apple...ne-means-gorilla-glass-2-likely-for-iphone-5/). There are other articles which you can google on your own.
Apple was probably using something like it but not the name brand version by Corning in the previous iterations of the iPhone. If you had zero scratches or no light marks with can been seen when tilted to the light then you are a very lucky person in a minute selection of the population.
Use a screen protector or not, I don't care but making statements like this to others with not only zero proof but also accusations that a person's product is defective is just ignorant.