@TexasToast:The HRs' job is more than hiring. They also need to handle staff benefits (medical and other insurance, learning and other allowances), staff payrolls (in big companies, their account department will request HR to calculate the data for them), exit interviews, etc.
In a company that I worked before, your department head can just norminate you for promotion but the final decision is from the HR manager (We had a System Administrator II got denied to promote to Assistant Manager grade because the HR manager said he has not been working in the company long enough).
Load up on WDAY. Imagine LinkedIn having verifiable employment history provided by Workday.