sometimes, when you ask a question as a rhetorical question, you don't have to follow the stress and intonation you are supposed to.
you have to follow a certain rule when your question really means a question, and you are waiting for a reply.
but sometimes, you dont need the answer, and that's why you change the intonation and stress.
and s.th else.
it has a close relation with your accent.
in my country, when we want to talk in english, we have to use all intonations and stresses correctly.
hope that helps, and i was correct