Yeah that's the problem... any kind of software-based feedback, whether it's a character appearing on the screen or a sound, can suffer from the same effect. And a dedicated processor for the keyboard to make noise? No. Laptop manufacturers are looking for ways to DECREASE costs of their laptops.
Of course there is a big issue I missed before... power. Last time I checked the LCD screen consumes the most power in a laptop, a problem that still (last time I checked) hasn't been resolved, although a few solutions are in the works none have made it to market yet (again, last I checked).
Anyways, it strikes me that adding a second screen (talking about as a keyboard, but applies to the first post too) isn't going to be too battery-life friendly. A traditional keyboard will easily be cheaper and lighter on the battery.