I don't really see how an employee directory could be considered a "trade secret"?

Head hunters use that information, companies don't want to lose valuable employees.

List of people, and their jobs, within the company? VERY useful information to competitor and hackers. You get to know the bosses secretary, by pretending to be friends with one of their friends - and you soon know everything about the company.

It IS NOT considered a trade secret. It is considered confidential information. That is an entirely different concept.

Confidential information like the employee directory could be used in various ways to disrupt the business or even the personal life of key employees.

Important members of the staff could be "poached" from the company if the directory was made public. or the employees of companies that have very vocal opponents could be targeted for harassment if their connection to the company was made known to these opponents.

Staff at women's health centers can tell you what happens when vocal opponents of a business know the home address of employees! Harassment, property damage, even death threats come their way.

In that case you clearly don't understand business: it is very definitely a trade secret.