This doesn't happen all the time. It is all based on the structure of the company and organizational hierarchy. The VP-HR or Director-HR reports to the CEO or the president of the company. In cases where the head of the HR department is not at that level, for example, if the head of HR is an Assistant Manager or Manager, then they are asked to report to the CFO or CTO.
In situations where the branches of the company are spread across the country or globe, the HR Head (VP-HR or Director HR) sits in the corporate office. In branch offices, they place Senior HR Executives, Assistant Managers, or Manager HR. In such cases, it is not possible for the VP-HR or HR head to oversee the work done by Executives or Managers at the branch level; hence, they are asked to report to the branch-head or operations head.
I hope I have cleared your doubts.
Thanks and Regards,
Sanjeev