It probably has to do with the fact that HR decisions don't have much of an upside. If you make a good hire, it reflects well on him. If you make a bad hire, people question your judgment.
You have an upside in hiring if you'll directly work with the people you hire. If you're in an entirely different department, there's no real benefit. HR is just the gatekeeper.
You have an upside in hiring if you'll directly work with the people you hire. If you're in an entirely different department, there's no real benefit. HR is just the gatekeeper.