Why d0 pepl wr1te rlly bad?

This type of "vanity plate writing" became popular when I was a teenager, something I've never done outside of IMs, and even then it was brief. The most common excuse is "I'm not at school, I don't need to write well", which reflects on their character as lazy and childish people who only do things well when they HAVE to and not out of personal integrity. It could be not true in their case sometimes, but that's always the impression I get. I don't mind spelling errors so long as it looks like they're making a genuine effort to spell things correctly, but deliberate bad spelling and an overuse of shorthand just doesn't look good.