Take a look at the distance between the fenders and the top of the tires. I've had several boat trailers like that, they flip the axle onto the other side of the springs. Why would someone do that?
A. So that when they launch or load their boat they have to back up the truck way into the water as well.
B. So that when they go off-roading the tires don't hit the fenders.
C. So they can look up their woman's skirt when she gets in or out of the boat when it's on the trailer.
D. They're getting the trailer ready for 24's.