It's a bit of apples and oranges. In a first person shooter the gun is your character that you see on the screen - so there's much more of a personalization impact if you invest in gun looks.
In Anthem, it's a 3rd person shooter with a zoomed-out camera, so we invested pretty heavily in suit personalization since that it what your character is on the screen most of the time. The gun is typically either on your hip or mostly obscured during gameplay.
That isn't to say there isn't opportunity there, just explaining why we went one direction over the other before launch.