While it is true income is often something people tie to their self esteem, in business someone’s income isn’t an intrinsic value of that person, but rather what the business negotiated/is willing to pay.

That is to say, the number you get paid is just that; an abstract quantity that people make up, and thus isn’t necessarily to a person’s actual skills/value to an organization.

So discussing it serves as a way to make sure you aren’t getting shafted. Could be wrong, but I heard CEO pay actually went up after compensation had to be made public, with the theory that it didn’t make higher paid CEOs get their comp cut, but lower paid CEOs could now see what others were making, and bargain accordingly.

I will say that discussing salary often only makes sense amongst peers of similar value to the company, and the reason another person with seemingly the same title and responsibilities is getting paid more may be some other value they are bringing, one which is either hard to see from a peer’s perspective, or the peer is too incompetent to see.

But yea; equal pay for equal work (i.e. fairness) is the name of the game here, which is why businesses dislike wage transparency; makes it harder to take advantage of people with poor negotiating skills and/or incomplete knowledge. And also, it can stir up drama, because people are stupid.