“…SMS language (also known as chatspeak, txt, txtspk, texting language or txt talk) is the English language slang used in mobile phone SMS. It is an abbreviated form of English known as a rebus. With predictive text input increasingly being used, it is becoming less common.

It is similar to AOL speak, and it evolved from the shorthand used in Internet chatrooms to accommodate the small number of characters allowed (early SMS permitted only 160 characters), and as a convenient language for the small keyboards on mobile phones.

Sorry becomes Soz, and Tomorrow becomes Tomoz (further abbreviated to 2moz and later to 2mz.” …

… a sample: “Hi mate. Are you okay? I am sorry that I forgot to call you last night. Why don’t we go and see a film tomorrow? (120 characters) .

……………

hi m8 u k? sry 4gt 2 cal lst nyt. Y dnt we go c flm 2moz? (57 characters – less than 1/2 the amount of original characters) .

As for why people say it, I have no idea.