I have always used fenders while touring on and off road. This choice was reinforced vividly on one tour.
I was approaching Quito, Ecuador from Columbia in a heavy rain when I started hearing sharp noises from something hitting the fenders as I rode. The noise was from discarded hypodermic needles scattered along the road shoulder for mile after mile and picked up by my tires.
I really appreciated my fenders even more than for just keeping me and my drive chain clean and dry.