Because if you don't share salaries, companies can negotiate 1 on 1 with every employee for salary. If their max budget is say 100k and individual employees neg

Because if you don't share salaries, companies can negotiate 1 on 1 with every employee for salary. If their max budget is say 100k and individual employees negotiate in the range of 100k to 50k for the same job, the company saves a lot of money. If employees discuss salaries, the 50k person will discover they're being paid half as much as a colleague for the same job and will demand a raise.