For every rockstar 10x developer who actually is worth much more because they are truly exceptional, there's probably a bunch of others that just happened to have good. career trajectory, or entered during a bubble peak, or have a better diploma, or the right connections, or are skilled negotiators or whatnot.
The hope is that salary transparency will bump their colleagues doing similar work at similar quality up to similar pay. The fear is that it can create workplace resentment, or lower everyone's wages, or invite retaliation, etc.
IMO those are short term growing pains that wouldn't last once transparency is normalized, like in government pay.
I'm sure all sorts of entities would like to know exactly what your income is.
But it will be useless because they cannot play with it. Even now they ask you what your pay was.
If I know exactly how much you make, I know exactly how much to raise rent.