I'm guessing, like Jeff said, they're randomized, pack-in junk. Not meant to be accessories, not meant to make sense as to which figure they come with...
Had they been, I think they'd be more popular. Same as the holo minis that Hasbro gave the SW figures for a while, would've gone over better had they been little holographs from the film, like a little holographic Rodian Senator for Palpy's desk, a little Holo Leia, a little Holo Vader, etc. But that's me... Maybe kids dig this crap.