To facilitate collusion.
Although I understand your larger sentiment. As a farmer, I have to align my prices with the Chicago Board of Trade, which in many ways is similar. Once price data becomes pervasive enough, there is a tipping point where you have to reveal your prices early to remain competitive. I mentioned retail earlier as being another example of where that has taken hold. That theoretically is a reason why rentiers could be compelled into using such a system absent of collusion taking place.
> but that is why our capitalist society discourages it.
I am not sure I understand the attribution to a capitalist society here. It was also discouraged to talk about income in Soviet Russia, as an example. That competitiveness of which we speak is not a function of a capitalist society, it is a function of human nature. Hell, I bet in early hunter-gatherer societies it was discouraged to talk about how much of the gathered resources you were able to keep for yourself.
What evidence do you have for this? In current "socialist" countries like China, talking openly about wages is common and not discouraged.
The incentives are crystal clear. Price coordination works, and workers in USA are brainwashed against doing it in their own benefit.
Again, price coordination is necessary to remain competitive once price data becomes pervasive. Such data is not readily available in the USA with respect to labour, however, thus it is a competitive advantage to remain guarded.
> No business wants to reveal price before they have to.
Interesting. If RealPage/etc is "just" about information sharing, as many of its defenders in these comments are asserting, why would any rentier use it? There must be more going on.
Anyway, coworkers or friends sharing labor price information clearly has nothing to do with your rebuttal. The main outcome is that one party might be inspired to ask for a higher wage. It's a crude form of coordination, but that is why our capitalist society discourages it.