That’s a truism - but I think we have it wrong. Why shouldn’t we be open with close friends and colleagues about what we earn? (Obviously as long as it’s not for bragging purposes)
IMO, it’s just a convention that developed in former times and will soon be seen as anachronistic.
As pay scales start disappearing from lots of companies having some sort of openness is a guide about how well your company is treating people, especially in similar roles. The advent of places like Glassdoor have a place, but more for people seeing other company data if they are considering job changes etc. Knowing where your own employer stands seems an obvious expectation. Like you and others mention, it's very much a thing of the past in some ways, data and the availability of data changes life again and things move on
NB: Doesn't excuse the premise of the original post and the article which is meaningless made up click bait rather than meaningful data from valid sources as evidenced by the disparity in the claimed figures and the published accounts
