why would you want grease on the splines of the FHB?
chain lube manages to work itself onto the splines no matter how meticulous a cleaner you are.
Prevents corrosion between metal-metal contact. Keeps moisture out between metal-metal area (this might not apply for people riding in either dry areas or fair-weather riders).
As to the second part your statement, this is not true--for example, people using SRAM Red cassettes.
Later.