Well, it all depends on the key of a song...
The B chord occurs diatonically in 3 keys, in one it is the tonic - B Major, in one it's the subdominant - F# Major, and in the last it's the dominant - E Major. Now, E Major is a rather common key, but B Major and F# Major aren't as common in popular music, therefore B Major is rarely used in popular songs, compared to the easier keys to play in, such as C, D, E, A, and G.
(I assumed you meant the B Major chord was rare, so if you meant all B chords are rare, I think B Minor is a pretty common chord)
"You must stab him in the heart with the Bone Saber of Zumacalis... well, you could stab him in the head or the lungs, too... and the saber, it probably doesn't have to be bone, just anything sharp lying around the house... you could poke him with a pillow and kill him."
- Aqua Teen Hunger Force, The Universal Re-Monster
