Hmm. I guess maybe this distinction makes up for the fact that in the original film (Star Wars) neither of the droids were properly recognized during the medals ceremony for the parts they played in the destruction of the Death Star. I get that maybe the necklaces wouldn't have looked right on Artoo anyway, but it is what it is.
For those wanting to explore the Robot Hall Of Fame, you can find it online right here.
As always, thanks for reading ... and May The Force Be With You!