Some teflon impregnated bushings require no lube and work better dry.
The use of bearings on rear suspension is not really the intended use of this type of bearings.
They never get to spin all the way around. Figure that you are spinning a cartridge bearing 1/4 way around back and fourth a zillion times. The ball bearings inside might get flat spots or notches from this action.
A long time ago I had a GT LTS that had bushings. This bike squeaked so bad that the LTS soon mean Like-To-Squeak.