There are two things, the size of the market and the price. Such a device will be pricey, and that limits the market even further. Another thing is that most of you don't want such a device after all, you are only constantly whining because your wet dreams of market domination by open devices get shattered - again and again. Unless you (the potential market for such a device) sober up, there will be no devices for you. Nevertheless, I am convinced that a profitable market do in fact exist, but all manufacturers are too blinded by market shares and dreams of world domination to notice.