I refuse to believe that they don't know they're lousy writers as those aren't easy mistakes, those are the errors of someone who is severely language-impaired.

I'm sure they know something is wrong with their profiles, except maybe the gratuitous-capitalization people, who probably think it's a great way to stand out. I think they're probably too lazy to bother getting it even close to right, think getting it close to right isn't important, or think the people who'll be reading these things either won't notice or won't care.