Oops! Indeed, I mis-perceived your comment as being a response to lotharbot's comment, about the tilt of right-hand pointing being an influence. Sorry.
However, I do think there's something more than "just so" to the darkmighty post you replied to, as well.
Anything that's hand-manipulated, and especially English writing on paper, must face the risk a dominant right-hand will partially obscure it. Thus we've got longstanding design tendencies, echoed on pixel screens, that more primary labels and information tends to be above and/or to the left, and more-ignorable (or even just defer-able) information goes to the bottom/right.
If damaging the visibility of some information for another purpose – as with an overlaid pointing indicator – a designer will thus have good reasons for allocating that damage in the down-right direction. (That is, tend towards obscuring the later/lesser information.) People immersed in our culture's visual design will even make that tradeoff subconsciously. So a "this makes intuitive sense" story, when reasoning about long-ago design decisions, is perfectly worthy of mention alongside other "historical evidence".
