This has been my experience. I've owned a ton of Apple devices and non-Apple devices. Almost every one of the Apple devices has been exchanged at least once because of a bad screen. I haven't done that with any of the other companies' devices (and I'm not less picky for those devices). Yet, I still love Apple stuff and continue to buy and exchange. Go figure.
I was thinking the same... Other companies' devices I've had and/or encountered (friends' and family's phones, tablets, laptops, etc) had perfectly uniform displays. After exchanging 5S four times, my display still has interlacing issue and yellowish smudge near the top.
It's not just iPhones... My iMac also has dark smudges throughout the screen (screen burn-in?). And bottom right portion is noticeably yellow.
That being said, I love Apple products. They have certain charms that other manufacturers can't offer. My mid 2009 MBP and iPhone 4 have perfect screen. And they still function very well (MBP still feels like brand new computer.) And my iMac is a beast!
I wonder how people would have reacted if other manufacturers' devices had similar issues. Could the same logic apply to these companies as well? "Not all phones are perfect", "no two phones are the same," "just contact the manufacturer and wait for the fix," "that doesn't mean majority of devices has the same issue,"
Imagine if one Samsung phone had the display issue. Would we call it a junk or say that it's only one bad apple in the barrel..? Which answer would be "over-generalization"?
That being said, we should be glad about Apple's service. Try exchanging other manufacturers' devices. They don't have strong retail chains like Apple, and it gets complicated when you try to exchange for a "perfect" device.
Exchanging Galaxy because you "think" screen is defective? Call the customer service. You'll likely be told to contact the store where you bought the phone. Then the store will tell you to contact Samsung... Then Samsung will say, well, "you're seeing it wrong." Haha. If you keep insisting that the screen is defective, they will probably set up an appointment at a third party cell phone repair store to examine your phone.
Imagine exchanging four times....