Introducing the iPhone...

[AgentZero]

Azselendor said:
I can't figure out why anyone would want to spend ten minutes typing out a text message that you can spend two seconds and call them with the bloody phone -- after all, that's what a cellphone is for!

I'd consider it a matter of etiquette. Phoning someone is sort of like saying, "Drop whatever it is you're doing and pay attention to me NOW!" which is rather rude and not considerate of the fact that the person might be busy at work, in the middle of class, or otherwise not available to take the call. Whereas a text message is sort of like saying, "Hey, I need to relay this information to you, but don't mean to interrupt what you're doing. Read this and respond when you can." Which is a fair bit more polite, don't you think?