Here's why. None of your reasonings make sense because as Duckman stated, why the clutch and not the brake?? Same components, same materials, same design. Except...
Unlike the brake system, as the disc in the clutch wear, (and along with the natural flow of fluid in the system) fluid is displaced into the reservoir. In a brake system, as brake pads wear and the piston is displaced further into the caliper, the fluid in the reservior decreases. With the clutch, the fluid in the reservior increases, bringing along with it, any contaminants, crud, or dust that happens to get into the system. If you'll notice, this is why you have a 'min' and a 'max' line on the clutch reservoir, but only a 'min' line on the brake.
We could argue how that gets into the system yes, but this is the reason it gets into the reservoir. If look closely however (at least best I have noticed on all three of my Ducs) the crud ends up in the reservoir stuck to the sides or resting in the bottom and not suspended in the fluid. I have never seen any detrimental effects from this, but I personally have never owned a Ducati that didn't do it.
'04 800SS...Strati Pipes, 42t sproket, DiD chain, Evoluzione fender eliminator, ABM Rotors, Carbon Lorane pads, Cogent-Dynamics Forks & Ohlins Shock.
'05 749s...Termi 54mm full system, 41t sproket, DiD chain, Evoluzione fender eliminator, PCIII/custom map, Pazzo Levers, Puig DB Windscreen, Penske Shock, CRS Forks, CF everything.
"Freedom, for those who fought for it, has a flavor the protected will never know..."