As discussed in the book, the rationale for removing the secrecy surrounding salaries is that

a$.$ we should be honest with employees, and this is a good place to start.

b$.$ consumers should understand that labour costs contribute greatly to retail prices.

c$.$ a more open pay policy will expose the inadequacy of the merit system.

d$.$ they know salaries anyway, via the grapevine, but secrecy reduces confidence in the company.

e$.$ positive motivational consequences may occur if the pay system is well designed.