Why dont dogs talk?

Because they don't have the mental ability to do so...

They can't talk because they do not have the right vocal cords. Parrots, on the other hand are lucky enough to be able to communicate through speech. Dogs unfortunately do not have aposable thumbs like primates or vocal cords that produce speech. They do understand commands, why not say something when we ask? Parrots are not just mimicers. They comprehend many basic things. They have the learning capability of a 5 year old child.