Security roles - Privileges vs. inherited roles

Summary

Why does a security have same function both as privilege and via inherited role?

Content

Some functions are added to a role both as privilege and via inherited role.

Example:

ORA_ORC_RECRUITER_JOB has "Update Job Offer" as a privilege, but the role does all include the inherited duty role "Update Job Offer", which only only includes the privilege "Update Job Offer".

Do you knoe why are both needed?  

Version

20A