Eh. It was created before 'continuity' as a concept was really any kind of concern. It's the continuity of soaps, ie 'what you can remember'. There was absolutely no need for any other kind of continuity until video recorders entered the home, and that wasn't really until the mid-80s. Which, funnily enough, coincides with the most fanwanky stories onscreen.

Retcons are the only way DW is ever going to make any sense at all :)