I think it's supposed to make sure it's a human trying to do whatever you're trying to do. I kinda like the idea that it assumes that a computer can't read wonky text, but sometimes they get really out of hand and even *I* can't read the wonky text!
But, what has caught my attention the most lately is not the weirdness of the text, but the text itself. Have you noticed the WORDS being used? Here is a sampling of the words I've seen lately (and yes, I am just that ana…um… METICULOUS... why?):
I bet I can outsupen you in the gulcater, but you'll have to resoze the hyperst or it will be a calumme! Don't tmentio it to your undster, just scrystsh the haliseab and we'll be gisel. Aedogi?
(Snesse!) Bless you!