Why dub Peter O'Toole's voice as an American?

I agree, Peter O'Toole should not have been dubbed. Was his English that heavily British-accented back in 1959? I think today in 2010 that mistake would not have been made and O'Toole's voice would have been kept, Brit accent or not. That said, at least the manly American voice selected to dub O'Toole does match O'Toole's appearance and did good credit to him. Still, no actor likes being dubbed, no matter how good the voice. The dubbing was done accurately so there's no Japanese-like humorous mismatch of silent moving lips. In fact, when I first saw the movie many, many years ago, I presumed it was the actor's real voice. Peter O'Toole was a much younger man in this movie and with his close-cropped beard, was totally unrecognizable from the clean-shaven, much-older O'Toole everyone remembers. More, in this movie, O'Toole kind of looked, well, rugged, macho, and handsome, as if he could turn on all the young ladies. If there was any movie where Peter O'Toole could point to being anything near a male sex symbol for women then this movie is it.

P.S. I should add that I missed the 'obvious'. Peter O'Toole's character is supposed to be a Canadian law enforcement officer. Canadians (except French Canadians) typically speak more like Americans than British. It would have been an obvious error to have a Canadian law enforcement officer speaking with a noticeable British accent.