As others have said, universities and government agencies generally publish their salaries in order to comply with transparency laws. Nepotism, for example, is harder to get away with if all salaries are publicly posted. But from the university's perspective, this has the potential to:
- Generate bad press, if a reporter feels (rightly or wrongly) that an employee is overpaid, and
- Give employees more leverage during salary negotiations.
So I seriously doubt that most organization would release salary information if they didn't have to.
By the way, it may seem like universities' opposition to transparency laws are entirely selfish, but let me make one counter-example. If Dean Bob's salary is triple the market rate, it may seem self-evident to an outsider that the university is not "using their tax dollars well." But it may be that the university has already concluded that replacing Dean Bob with three market-rate deans would be a net detriment to the university; Dean Bob is "just that good." In this case, the public outrage at Dean Bob's salary would be entirely misplaced, and the university would be forced to choose between doing the right thing or doing what looks good. This interesting Ted Talk gives a good discussion of this phenomenon as it applies to charities.