> If it's just an update, then why not just keep calling it "the iPad", without appending a Big Shiny Version Digit?
Because eventually there's going to be an iOS version or an application that only runs well on version X of the iPad. It's a lot easier for a user to understand "Only works on iPad 2 or better" then to understand "Only works on iPads manufactured on or after March xth 2012".
It’s a slightly different situation but that’s essentially what they are doing with Macs, saying this-and-that is compatible with the MacBook Pro (early 2009) and such.
It is also common to refer to the Macs with their iteration+variant number, e.g mine is a MacBook Pro 5,5
System Information was actually the easiest way to get such a specifier before Lion, which now shows the "MacBook Pro 13-inch, Mid-2009" in the brand new "More Info..." of "About This Mac".
Because eventually there's going to be an iOS version or an application that only runs well on version X of the iPad. It's a lot easier for a user to understand "Only works on iPad 2 or better" then to understand "Only works on iPads manufactured on or after March xth 2012".