As someone who used to have to pay for messaging fees, I've found that shorthand was very useful in keeping the cost down as what would usually take 4 text messages under normal grammar and spelling rules could be easily cut down to 1 or 2. It was also a pain in the ass to type out full words on a phone's keypad (8 44 2 8 0 777 33 1 555 555 999 0 7777 88 222 555 33 3). Now that unlimited text messaging plans and full qwerty keyboards are nearly ubiquitous, I don't bother with shorthand anymore as it even grated on my nerves when I did it out of necessity. Now it just shows lack of care and laziness to continue.
I guess my emphasis on the examples was mainly on shorthand but we can't ignore the staggering amount on people, adults, that spell incorrectly at least 6 out of 10 words. No statistics or anything on my part, just experience within the professional and personal spectrum.