USS Kearsarge prepares for flight operations....photo by Mass Communication Specialist 2nd Class Hunter S. Harwell

ATLANTIC OCEAN (Aug. 4, 2015) Sailors prepare for flight operations on the flight deck of the amphibious assault ship USS Kearsarge (LHD 3). The Kearsarge Amphibious Ready Group and the 26th Marine Expeditionary Unit (26th MEU) are conducting a composite training unit exercise in preparation for an upcoming deployment.

Off topic question.

Why does the Navy include the MOS of individuals when it comes to rank?  Is it simply tradition or is there another reason.