On several occasions, when I mentioned proper spelling was important for writers, I got the same answer: The spell checker should take care of that.
The problem is, it won’t. It will take care of some typos, but it won’t tell you it should be their, not they’re.
Last night, I found this wonderful poem. Have fun reading it — and trying to decipher it in spite of no mistakes a spell checker would find (click on the picture to make it bigger and clear).