"The show has dragons, who cares if the accents don't match?": Well, first of all, I care. Second of all, the cornerstone of science fiction and fantasy fandom is nitpicking. Third of all, the fact that Game of Thrones doesn't take place within our collectively agreed-upon reality doesn't release it from its responsibility to verisimilitude or the maintenance of internal consistency within its own systems.
From Max Read's fantastic article nitpicking the inconsistencies in Game of Thrones' deployment of regional British accents: