Pretentious people on the internet frequently abuse this mechanic to make themselves look smart.
Proper grammar IS NOT a gauge of intelligence. Why don't more people use perfect grammar on the internet? Becuase they aren't writing academic papers online; they're writing in colloquialisms which other people understand. Many smart people talk colloquially because THEY ARE PEOPLE WHO GREW UP IN SOCIETY.
And if you find the need to prowl around the internet, fixing people's grammatical errors to make yourself feel good then...you don't recognize that ultimately, the English language is meant to be used as a form of communication, and not a way to make yourself look smart.
tl;dr : people rnt complete dumbshits just bcuz they type like this so stop being such a grammar nazi
Person A: Your wrong. Your argument is compltely flawed because of A, B, and C.
Grammar Nazi: IT'S "YOU'RE", NOT "YOUR" AND YOU SPELLED "COMPLETELY" WRONG. Therefore I have proven that your level of intellegence is so far below mine that it would be a waste of time arguing with a Neanderthal like you. No, I HAVE NO IDEA WHAT AD HOMINEM IS.