"Recommended" is also 'required' if you wish to be covered by warranty...and after that warranty runs out if you wish to be covered by liability of design from the OEM
One of those 'can' vs 'should' vs 'rated for' language mix-ups...A half ton 'can' and did tow a curb (stripper) Space Shuttle...but is NOT rated for that 160,000 stripper model shuttle. Plus it will not tow it for long before it's wheels fall off...nor can it 'manhandle' that during an emergency situation...
Me too...won't fly on any plane serviced by a mechanic that believes in not servicing brake fluid...even though an aeroplane brakes only see a few hundred to maybe a few thousand (private vs commerical) miles in it's lifetime...
More than just being a sponge (hyroscopic) for moisture out of the air (via the bleed holes and even those MC reservoirs with bladders...or whenever the cap is opened to check fluid...gets moisture in there) that reduces the fluid boiling point (turns the fluid into steam and a gas pocket that is compressible) to reduce all the way to eliminate braking all together
That H2O in the unplated braking lines will have it rust. Both flakes of rust to mess up the seals and the biggie...thinned out the tubing that may burst or leak (loss of braking power) at the worst time...when you try to nail the brakes...