I started working as a PT staff at a well known clothing brand as I only had to attend 2 classes a week last semester.
It just so happened that during that period of time, there was a huge shortage of staff and in their desperation they advertised pretty high pay for us part timers.
HR told us to keep details about our pay to ourselves.
However, I thought that was bs so I didn’t take it seriously.
The store’s manager came up to me to have a chat when the store was quiet and we got on the topic of pay, turns out I was getting paid significantly more that her (she’s been working there for 4 years now).
Two weeks later, a bunch of staff came up to me to thank me. I was lost, but was then promptly caught up.
Word spread about my pay and HR had no choice but to increase everyone’s salary under the guise of “a job well done”.
tl;dr: keeping pay confidential is just a ploy to save your employer money and it’s bs.