Right because the original iPhone had less bells and whistles than all the other smartphones at the time.
Ironically, it did come with less than other smartphones of the time. No MMS, no videocam, no GPS, no 3G, no third party apps.
(Like others, I was using a WinMo touch phone at the time with Google Maps, tap-to-zoom Picsel browser, Slingplayer for remote TV viewing, etc.)
But that's a different discussion.
I think it is horrible idea. It increases the cost, size and chance of breaking something while decreasing the battery life. I'll pass.
Of course, most of those happened with the slim iPhone 4 glass back as well. (Cost more, took up battery space; more breakable.) Didn't stop buyers
An e-Ink second screen would actually increase battery life for a lot of users.
Sorry. Just being the devil's advocate today.