There is a parallel universe where the convention is that 0 is used for when something went wrong, and 1-127 are reserved for all the myriad and beautiful ways in which things went right.

Indeed you're supposed to, but that way if someone calls exit(0), it looks like the program worked fine, when in fact they committed some debug code and made the program no longer run to completion. "Yay, done" was put in for the scripts to flag this sort of thing, presumably based on experience.