Yeah....plenty of reasons. You get good weapons sometimes from rank up packages. I got a 299 hand cannon from my last rank up. Also whatever rank you are means you get to choose from that many different rolls on the weapons you order on armsday. So if you were rank 3, you would get 3 choices of rolls & sometimes elements on your ordered weapons. Also ranking up the gunsmith is the only way to get the class specific weapons......the quest for the class specific legendary comes at rank 2 & exotic at rank 3.