Yeah, but that's a balance like everything else. It's far too easy to end up somewhere where the complete design requires added complexity to figure out the st

Yeah, but that's a balance like everything else. It's far too easy to end up somewhere where the complete design requires added complexity to figure out the state of the multipurposed pins (and that associated logic's additional pin count) that you end up with a harder to manufacture product. Edit: adding that this is in the late 70s/early 80s where final integrators were using a bunch of 7000s-esque logic to glue the board together. Nowadays of course we can assume so many transistors on both sides of a trace that super generic sets of SERDES-style pairs makes sense nowadays for most complex buses.