Threats vs. obligations
Security asks how to protect data and systems from adversaries. Privacy asks what an organization is legally and ethically permitted to do with personal data in the first place. The disciplines cooperate constantly and are not the same job, the same skill set, or the same career ladder.
The CISSP certifies the first discipline at the senior level. The CIPP certifies knowledge of the second: the regulatory landscape, data subject rights, lawful bases, transfers, and enforcement. A CIPP holder is not certified to secure anything, and a CISSP holder is not certified to interpret privacy law.