The obvious reason is the form factor - many buttons are squeezed onto a small object which must fit smoothly into a pocket. But more subtly, it suffers from computer syndrome—any object, combined with a computer, behaves like a computer. That means it is probably excessively complicated in design and interaction, that is probably crashes, that it is certainly not simple and perfectly suited to the task.

Consider, then, the Siemens GigasetSL1. It's a cell phone posing as a cordless phone. I already hate cordless phones, because they introduce pronounced unreliability and battery limitations for inadequate gain, particularly in an office environment where a cord is a negligable problem. But what makes the GigasetSL1 an astoundingly awful idea is that it carefully husbands all of the limitations and design compromises of cell phones into an application where they are completely unnecessary. Office phones, which don't have to move frequently, can offer large displays, sizeble and well-labelled buttons with dedicated functions, and in general a less computer-like interface. Instead, we get the short end of the stick - all the drawbacks of a cell phone traded off for ... nothing.