They are pretty standard on a lot of Hondas, I don't know about other brands. I have respect for Honda's legendary build quality & engineering, so I figure they put them there for a reason (mass damping). YMMV
I've found having damping of bar-end weights actually helps on track. It calms down vibrations and lets me get better feel for what front-end's doing. When you're nearing traction limit, front-end goes slightly numb and you can feel it as lightening up at bars. Without vibrations, it's easier to feel this change.
My race org requires brake-lever guards, so factory bar-end weights have to come off right side anyway. I just machined 250gm lead slug from fishing weighs to fit snuggly inside bar further up. Then lever guard goes on at end.