and that is the best reason. if you are a hunter/huntress, and use a bow or gun (I do know trolls who only use throw, which is cool), then it may be worth the slot. Since hunters usually don't have to cary multi sets of gear, then it is not so bad, if your other bags are big.
Note also that sometimes a ammo pouch or quiver can be had as quest reward, too.
on a related note, there is a big discussion of speed vs. damage. Blizz has balanced it out, mostly, but I have always preferred speed. it is most imp. for when a mob chooses to run - a hard hit bow or gun is no good if the enemy can get out of range.
