Well, that's based on experience and several close family members who have worked in Ministry positions.
When you have someone who has good work ethic and a desire to make a difference, like my sister for example who worked for the Ministry of Education, that only lasts for so long when you are the minority in that regard. If you are stuck in a pay bracket, no bonuses and aren't getting personal satisfaction or a feeing that your contribution is making a difference then what reward are you getting for your efforts?
Would you stay were you are if you weren't being rewarded for your performance, whether monetary or otherwise?