While I don't necessarily believe in the specified frequency of fluid changes for motorcycle clutches and brakes, it is a necessary evil. Brake and clutch systems are not actually air tight, they can "breathe" ever so slightly through the master cylinder and seals, over time. Brake fluid is hygroscopic...it absorbs moisture from the air it comes in contact with, even a tiny bit of air in the top of the master cylinder or through pores in the ferrous castings so small that they will not even leak fluid. Brake fluid also collects contaminants over time. With small system volumes on motorcycles, these contaminants and moisture become more important...and more damaging, than in a large system on an automobile. If you do not change the fluid periodically, you risk eventual corrosion of your brake or clutch system, as well as wear from any contaminants. How often you do it depends on your climate, your mileage, how hard you use your systems, and the quality of fluid used. I still recommend periodic changes, however.
Another consideration for those with extended warranties is the fact that any brake or clutch system hydraulic failure will probably not be covered if you choose not to flush the clutch and brake systems. Now, if the procedure just didn't require BUDS, it would not be that tough...with the right equipment. This is not an uncommon requirement under motorcycle maintenance procedures, and is even specified periodically for most autos. I have had to do it for my BMW, too. Overkill...maybe, but justified, considering the possible consequences and the importance of the system. There is no dual system on a Spyder!