Because salaries are much higher in the private sector. Some is no doubt job security. However, as Herzberg notes, there are many different motivators. In fact, some things don't motivate us at all. The fact that they exist simply makes the job acceptable.
Motivators are something else again.
Herzberg argues that motivation has a good deal to do with the way jobs are designed, with responsibility being given to employees, together with opportunities to collaborate with others in collective decisions. This entire topic relates in very interesting ways to literature on community policing, community corrections, and community courts. The discussion of motivation is not at all settled. In many ways, it is an ongoing debate. As we will see in both the lecture on Herzber g and the next lesson on employee satisfaction, there are many things organizations can do to motivate employees without costing the organization a penny.