More incorrect than rude, typing is about hitting the letters you wanted to hit accurately, quickly, consistently and without strain or injury, spelling and grammar are something entirely different!
And both are about communicating with other human beings effectively. I could spell out everything phonetically or use text shorthand as well, but that makes it generally harder for a wide audience to enjoyably consume my writing. Humans do a large part of reading via gestalt comprehension, changing the "shape" of words stymies this process.
