They would lose more money and time refining the hardware or in warranty repairs. They said 'no warranty' for a reason - probably the same reason they replaced it with a unibody device where nothing can be replaced (so not much can go wrong).

It's a sensible idea considering a qwerty keyboard doesn't sell a device (see sales of Android devices, as an example). It's just a disappointing one, considering I don't think I can bear using an eyes-free input device for my main phone.