I think you will find all Douglas tricycle landing gear aircraft have canted nose gears (DC4 thru MD11). I always understood it was for caster similar to a bicycle or motorbike. On Douglas aircraft the center of the nose wheel axle was mounted on the centerline of the inner cylinder whereas other designers used a trailing axle to achieve caster ie. the axle was behind the centerline of the oleo strut thus obtaining caster effect like a trolley wheel.
Having said that I don't know why the A320 family is the only Airbus product to use a canted nose gear.