texting is a form of asynchronous communication who places the greater burden to the sender who has to spend more time typing a message, while a phone call can be faster.
But, text messaging is considerate to the receiver, as it lets the receiver consume the message at their own time, while a call would have to interrupt the person whatever they are doing.
Text is better in very noisy environments, bars/clubs/concerts.
In Europe at least, texting as always been a little bit cheaper than a phone call, and the receiver usually doesn't pay for received messages.
But it's more than just convenience. It's also the impersonal part of the text that makes it so popular. You can write stuff in text messages that would be wierd saying out loud.
Just like me writing this message to you - I can think about what I am writing, revise it, etc.
Communication is wide and varied, and SMS is a choice in communication. Trying to replace SMS with voice is like saying that one should replace email with telephone calls. The applications are different, and people use it for a different type of communication.