Why is it so bad to do it with a keyboard? a keypad is basically just a tiny keybord desu so I dont see the difference.
you've got a couple different types in the pic
the leftmost one is an accounting style keypad. notice the 00 key, that's usually for accounting..the "cents" key
it's set up like a desktop calculator so it's for speed in number crunching.
some keyboards don't have the extra "10 key" built in, you can position it exactly where you want (good if you are entering receipts and stuff) and you can get different key-switches from your main board if you like a different feel when 10keying
like the other posters have talked about, the gaming style keypads aren't just a keyboard sawed in half. They are pretty heavy on programmability, usually at that level with the stuff being stored onboard the pad which is really nice if you are going to a workstation that isn't one you customized. you bring your pointer and keypad
I come from the old summagraphics digitizer tablets where the puck had about 16 buttons so there are a lot of button functions you want under your hand, not on the main keyboard (and you don't want to be mode switching your main alpha-numeric board so much) . now that ppl don't use the digitizers so much, but use a mouse, having those extra buttons somewhere is awefully nice (I've used gaming mice for that, and drafting specific mice will still have a 3rd button not on a scroll wheel)
I think the main take-away is that they aren't just the left half of a keyboard slapped in case
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FWIW I've heard the 3dc spacemouse -s/mice? are touchy
not unreliable or touchy in a bad way, just that they expect a light touch so there's a learning curve esp since linear push and tilt are really similar motions
but that's just scuttlebutt I haven't used one
It might be one of those...suffer for a week and you're good type deals