Can’t you also ask your co-worker if you care to know?

My thought is this also risks creating unnecessary resentment in the office. (Most people will react negatively finding out a colleague makes $10k more, even if that colleague has more years of experience - people don’t think about compensation rationally)

For most large companies you can already research what the average salary is for a specific position on sites like glassdoor.

Taking privacy away from people and giving them something of no value to them in trade is a poor justification for change.