If WC Fields ever said that he was quoting it from GK Chesterton. Which a lot of people do frequently, myself included.

I'd be inclined to doubt whether country dwellers are any more likely than town-dwellers to be over-credulous and pig-ignorant about these things. Not without some figures to prove it.

There's an old saying "There's none so blind as those who will not see", and I suspect that supplies the explanation for this phenomenon.