Shouldn't be hard unless you mistakenly assume that your experience is indicative of overall trends (it never is just as one data point never defines a trend).
Even "all the ones I've seen" are statistically irrelevant.
"All the ones I've seen" / millions of iPhone 5's sold is pretty close to 0.
I see what you're saying...it's statistically irrelevant to use anecdotal evidence. However, the chamfered edge on the iphone 5 shows scuffs extremely easily. I can say this just as readily as I can say that most car windshields will eventually get chipped by flying rocks during their lifespan. If you're truly not protecting your phone and you've truly had it since September with NO visible white marks on the chamfered edge then that's very surprising. I'd place a million dollar bet that your example would be the exception.