Smaller sprocket = more ground clearance, but the real reason.....Because I can.
Add to that you can lower the sprocket/cvs in the chassis and get a better angle on the cvs (actually reduce the angle at static ride height) and there fore get more useable droop which is just as important as bump.
Again totally agree "cause you can". Large part of my reasoning for my final drive design as well.
Eg
First pic is the standard system from my chassis second is the new system, both are about where they would be at static height, see the axle angle difference. (this a rough approximation but it gives you an idea of what im talking about)