[ghaff]

As others are saying, it's the norm in some places and, in the US, it's common among government employees (who have more rigid pay scales anyway). Of course, highly paid individuals including the top-compensated people at public companies and pro athletes also have public salaries.

So it's not really some deep dark secret. That said, if a bunch of big companies in a place where public salaries aren't the norm decided to make everyone's salary public one day, you'd have a huge amount of blowback and it would be followed by a whole lot of internal gripes from people who think they should be making more than "Joe" is.