I actually think that text has a fairly high information density rate compared to iconography. The perfect example of this is the command line. Power users tend to prefer a terminal because it is more concise than clicking around in a gui. I think that the problem lies in the fact that we have very few universal icons, especially for something like a phone interface. This means that while an icon for 'unread mail' would be smaller than the text describing it, no one would know what it meant without a description. Since there is no real limit to the actions we want our phones or computers to perform, text seems to be the way to go. Of course, some actions (e.g. save, cut, paste) have icons that have been in use for so long that it might be fair to call them universal. You can see an example of what I mean in most mac os x applications, where the buttons generally have icons with labels.

Disclaimer: I work for microsoft, but nowhere related to the phone team.

Edit: My point is more about interfaces than design. I know nothing about typography.

I suspect that writing text to convey information to the computer (command line) has very different trade-offs than programs presenting information textually to users, and lumping them together probably misses important details.

Also, textual interfaces usually make it easy to say, "now group that set of operations and give it a convenient name" (scripting), while graphically interfaces usually don't, and users are stuck with whatever individual actions the UI designers added to menus.

Neither tendency is inherent in using text or graphics, but it usually works out that way. I've wondered about this for a while, but text vs. graphic interface discussions ("keyboard vs. mouse", which often overlap) usually miss that distinction, much like they do "approachable to new users" vs. "efficient for committed long-term users".