There's a vast swath of people who don't want to use curse words for various reasons, and how terrible it would be to accidentally insert "fuck" in your work-only phone!
Besides, we aren't all super coordinated with phones. I've been typing on these keyboards for two years now, and I wouldn't be able to live without auto-correct. I'm guessing that, since you are such an expert of using the keyboard that you apparently never misfire, perhaps you ought to roll without auto-correct? I know a few people that do...