historical accident of qwerty keyboards

Not an accident at all. They made the qwerty so that the common patterns of keystrokes would be far apart so that the typewriter wouldn't get tangled up as easily.

True enough, xara, but one presumes that there were a number of ways in which this could have been done, so the particular arrangement we have is, to that extent, a matter of chance. More importantly, however, there was the opportunity to change to a more rational scheme (a simple alphabetic one, if I remember rightly) that we missed because the winner of a touch-typing competition around 120 years ago happened to be a man who used a qwerty keyboard. As a result, qwerty became established (for speed! not for slowness!), and is now ubiquitous (except, as we can see, amongst linotype operators).