Words that are spelled similarly should (maybe) sound the same, but:
"I take it you already know
Of tough and bough and cough and dough?"
Quoted by Vivian Cook and Melvin Bragg 2004,
by Richard Krogh, in D Bolinger & D A Sears, Aspects of Language, 1981,
MacKenzie was telling me about the difficulty people have learning the English language. She has taken a bit of French and German.
She pointed me to a couple fun websites that prove her point. If you want to look at a few poems that point out the oddities found in our spelling, look here.