master on your local repo is a different reference to master at origin and master at other developers machines. By merging your master into origin/master instead of rebasing, you leave the history looking like multiple branches were merged together.
By rebasing onto origin/master instead of merging, you leave the history looking linear.
Ultimately it's about aesthetics, you don't gain anything by rebasing (when pulling) other than a cleaner history.
I'm not certain this is due to the particulars of the workflow of the team I was working with, but one of the benefits I saw of rebasing over regular merging was that rebasing let us resolve conflicts at the point of the commit in which they emerged, rather than in a merge commit at the end.
By rebasing onto origin/master instead of merging, you leave the history looking linear.
Ultimately it's about aesthetics, you don't gain anything by rebasing (when pulling) other than a cleaner history.