Nothing good comes from knowing other peoples salary. Only jealousy, resentment, unhappiness, and greed.
The key is having information specifically to formulate your company's BATNA. The notion that salary sharing is bad for the employee is hogwash from unfair labor practices developed over decades.
Would you buy a car from a dealership if the dealer told you "you shouldn't comparison shop it will only make you resentful"? Yet we are willing to accept that claptrap from a company. Not in this lifetime.
You know--things that any worker should want to know.
In 2 previous jobs, I found out what others at the company were making. OK, they were managers, but still, it just made me pissed off. It didn't make me happy by any means.
As others note, people tend to generally think they're above average. Can you not see that exploding their delusion might not be such a great idea? Some of them have to be below average. A team who doesn't share salary info, can all be happy that they're all above average. If they start sharing salary, half will be below average and probably pretty pissed off.
The people who benefit, are people who are generally happy as they are. Would you like to know how much money your neighbours have? Why should it matter?