On the other hand, a smart phone has limited battery life, would be severely damaged in a good rain, and would likely get a cracked screen if it ever fell off the bike, or even if the cyclist took a tumble. The bicycle phone mounts I have seen look suspect. Most of the mapping and routing options are web-based, which requires significant data use. Of course, this last point is not important if one already has a hefty data plan for other purposes. (I don't.) Even without the cost of the data plan, the value of web-based services is limited when no cell signal is available, as can happen on tour.
Having a phone on a tour is important. I own one phone, which is a smart phone. But it is a bit of a pain due to my desire to protect it. To answer the phone, I have to pull over, open the water proof handlebar bag, unzip the pocket, pull the phone out, and punch the screen. My chances of answering a call are about 50 - 50. Most times, I would rather continue the ride and look at the voice mail later on.
Being a technology enthusiast and a cycling enthusiast can be a lot of fun. There are great synergies available. But sometimes the combination just doesn't make sense, at least to me.