My guess is that the popularity of these professions is that they are all relatively low-qualified ones suitable to people working while studying or "filling gaps" before getting a "good job" in IT.
>Wouldn't the more apt comparison be something like law? Or medicine?
It could be, but I doubt that there are many people that after having invested in an education in either law or medicine and actually had a suitable job in those professions left them to become a full-time programmer, particularly an employed full-time programmer.
Not that it cannot happen or that never happened, but surely it is less common, and the probabilities that additionally these people will be commenting on HN are even smaller.
>Or has software development truly reached blue-collar status and we're essentially plumbers/electricians?
Since every other guy here seems to be well in the hundred of thousands US$/year or more, I would say, if this is the case, "exceptionally well paid plumbers/electricians".