There are people who say that it is easier to type like that, that its faster and whatnot. They claim that just because they type like this, doesn't mean they're stupid. They are wrong.
Look at the situations where people type these things. On a forum, the guy who spells like a three-year-old is spamming all over the place, breaking rules, and pissing people off. They post one-liners in RPs and debates, brag about their '1337 |-\4x0r or 64/\/\1n6 5k1llz,' claim they can delete your account, etc. In FFXI, they suck at their job, have crappy equip, brag about their level 75 char, claim they're friends with a GM, and beg for gil. Hell, if I got a /tell that said "Pardon me, miss, but could you loan me 200 gil? I just got back from farming, and I'm barely short of that new sword I wanted..." I'd be tempted to pay up. "OMGZ cn u giv me gilz?!" just gets them a baghnakh in the eye.
I should write up some sort of conclusion for this post, but I'm tired as hell and my brain is dumbed down by reading all the 'oic, r u ok?' impressions in this topic @_@