Wireless bandwidth is precious, airtime is typically expensive, LCDs are tiny, data rates are slow.
And, just as importantly, wireless operators are overwhelmingly voice-centric. The wireless industry has a miserable record selling any wireless data services. Most people in the computer industry haven't a clue as to what is required to produce a service that's valuable to wireless customers. It's a very tough market. I believe in the future of 'smart' devices.