It is a camera they have with them (handy for the impromptu photo or video).
If you watch any "behind the scenes" shows, the pros shoot quality programming using a big preview screen (bigger than iPad). Being able to see the finer details of what they are shooting means getting a better photo or video.
This device is trying to evolve into an everything device: don't need a separate camera, remote control, phone, computer, music player, portable movie player, GPS, internet-connected device, etc. Lots of functionality in one device.
Have you seen the apps that use it for stuff other than photos or videos? For example, there's travel apps where you aim the camera at a sign written in a foreign language and it translates that sign to english. There's check deposit options where you can deposit a check without going to the bank by snapping a picture of it. Download Star Walk and go outside at night, aim your iPad camera skyward and the app tells you the names of everything you can see. Etc. There's lots of utility for giving an iPad an "eye" beyond just taking photographs or video.
Lastly, not everyone has an iPhone. So assuming iPhone makes many functions available within an iPad redundant. Perhaps one should argue the iPad should be cut down to just a bigger screen ONLY for iPhone users who want to stream iPhone images to a bigger screen (a "dumb screen" iPhone companion if you will)? The better choice is to assume that not everyone has an iPhone: then think about what needs to be in an iPad. If I don't have an iPhone, I want a lot of iPhone functionality in an iPad.
I'm with the other guy above: if the whine is about saving $5, I'd rather pay the $5 and get the camera (something like that Star Walk or visual language translation benefit is mind blowing if one cares about such stuff). Several retailers will regularly discount iPads by a few bucks (like $5). Buy yourself one from there and put a piece of duct tape over the camera hole. Save $5 and end up with the exact same functionality- or lack thereof- you seek.