Why do iphones have broken glass?

I've owned many different smartphones, never an iPhone though. I've noticed that a LOT of iphones have had the glass break, and it seems to be far, far, far, far, far, far, far, far, far etc. More common among iphone users than among users of other smartphones. I myself have never broken any of my smartphones that way, so I wonder why it happens to so many iphone users?

Also I do not accept the theory that more iphones than other smartphones are the cause, cause the numbers are just way out of proportion for that to work.

Models before the iP5 lacked the Gorilla Glass that was a feature of many competing models. Also, iPhones until recently had heavier metal bodies which hit the ground harder, and glass which ran right up to the edge of the phone so was more vulnerable to damage. They are also generally quite thin and sleek which makes it far easier for them to slip from hands, pockets and bags.

Until the Retina Display models, the phone screen was behind a separate protective glass layer which could be replaced separately if only that part was cracked. Later models bond that glass to the screen to reduce reflections, and use Gorilla Glass 2, but if it does break the entire Retina Display panel has to be replaced and it's not cheap.