Originally Posted by
qei
Because the reward is your rating, not the conquest point. Anyone who is serious about arena doesn't play until he is conquest capped, but he plays until he has the rating he was aiming for. Compare it like this:
Battlegrounds = Heroics
You do these to gear up and get ready for the real stuff, such as Arena / Rated Battlegrounds (or Raids)
Arena / RBGs = Raids
This is where the serious, competitive stuff goes on.
Besides, if Arenas gave honor it would make Battlegrounds completely useless (unless Arena gave such a ridicolous amount of honor, but that would just make Arenas giving honor after CP cap pointless in the first place)