My first iPhone 3G, I used it without a case. When I got 4/4S I got a case for them, for the reason that can be amusing: those models got a pretty decent camera

My first iPhone 3G, I used it without a case. When I got 4/4S I got a case for them, for the reason that can be amusing: those models got a pretty decent camera so the case was meant to prevent scratching the glass covering it. iPhone 5 got sapphire cover on the lens, so I intend to go case-less again.