Don't think anyone can explain except to say it's Apple or Steve Jobs. They do what they want and no body can seem to understand why. Like Blu-ray (but that's another whole thread on it somewhere else)...
Or as usual (or often the case), look else where for third party solutions. eg.
http://eshop.macsales.com/item/Cropmark/8337/?utm_source=google&utm_medium=shoppingengine&utm_campaign=googlebase
The Amazon (UK) reviews for the numeric keypad are horrible. Reviewers describe it as plastic, tacky and unreliable. It's also expensive £37.99, when last I looked. Which I think is a lot just for the numeric keypad. You can buy the whole thing (albeit wired) from Apple for £40.
But thanks for your contributions, guys.
Why would you need a full sized desktop keyboard to be wireless? It's too big to lug around with a laptop and it's not the sort of thing that moves around much on desk.
For four reasons. Firstly, the convenience of not having to worry about a cable. With a wireless keyboard you can have it wherever you want it; on the desk, on your lap, on the arm of the chair, and you don't have to worry about the cable being too long, getting tangled, or knocking drinks over.
Secondly, when you're not using the keyboard, you can move the whole thing out of the way without detaching a cable.
Thirdly, repeatedly plugging and unplugging things into the back of an iMac causes lots of scratches by the USB port if you're not very very careful.
Fourthly, when entering numbers on a spreadsheet or a table, a numeric keypad is much much easier. That's why they exist in the first place.
They used to have a wireless full size. I do like the bluetooth extension that someone made.
My guess is if enough people request it they will make it. Maybe in the next revision.
Fantastic idea.
Click on the link below to suggest a "product enhancement" of a wireless keyboard with numeric keypad.
http://www.apple.com/feedback/imac.html
I'm sure Tommy060289 is right
it's simply a case of Steve's House - Steve's Rules!
But if we don't ask, we won't get.