Although some managers are good communicators and essentially all leaders are good communicators, over time, employees will take their cues and develop their opinions from what a manager does rather than what he or she says. In a way, this is not unlike children who, over time, will emulate what their parents do rather than what they say.
Obviously, the employee-manager relationship is not a child-parent relationship, but there are elements that are similar. A good manager may also be a good coach or mentor. A good manager may “care” for his or her employees in a protective way. A good manager may work hard to help the employee mature and develop. Those are all reasonable components of an employee-manager relationship.
Nonetheless, managers and leaders who are most successful at getting their employees to follow their guidance also tend to be very consistent about modeling the same behaviors. If a manager wants an employee to be “professional,” but tells inappropriate jokes in the office, the employee will follow the behavior instead of the words. If a manager insists that an employee focus on maintaining a better work-life balance, but the manager stays in the office late and doesn’t take vacation days or won’t stop communicating with the office when on “vacation,” the employee will follow the behavior instead of the words. In short because of the power dynamic inherent in manager-employee relationships, it is the manager’s behavior that becomes normative.
Like many things in management, this is as much about basic human psychology as it is about organizational dynamics or management tactics. If you want employees to emulate certain behaviors, then you better behave that way yourself!