I know that the term "rights" applies to users or groups of users (such as "the user X has the right to change system time") and the term "permissions" applies to an object (such as a folder or file, e.g. "the user X has full permissions over this folder"). This link says the same.
Then why are we not saying "user permissions" instead of "user rights"? What is the difference in the meaning of the two words "permission" and "rights"?