There is no functional value to pronouncing them differently when there's not even a consensus on how they should be pronounced when you do. Oh, he said dahhhn? He must mean Don, unless he's from this part of the country, then he might mean dawn. Oh wait, he said dawwwn? That probably means dawn, but it might not. Or maybe he doesn't even pronounce them differently, but when he's asking a question he says it more like dawwwn but if he's stressing it at the start of the sentence he says it more like dahhhn.
No matter who you are, unless you're locked in your hometown with other people who share your exact hillbilly accent, or annoying English speakers with your jersey shore new York accent, you're going to have to use context to discriminate. And it works just fine.
those of you arguing for these things to be pronounced differently are just demanding that the rest of the world mispronounced things the specific way you prefer because you're incapable of figuring things out on your own. It's a failure of the education system I guess.