Now that smartphones are ubiquitous, what's the point of SMS? Everyone has fast, easy, mobile access to email, which has none of the limitations of SMS (message size, tied to a device and not a person, etc.). Email, you can access on your phone, your PC, your tablet, or even a public web terminal in many cases. It even lets you communicate to someone without a phone!
Email requires you to have an email server, which either you or someone else (read: google) must host.
All you need for SMS is a phone number. No middle man.