Doesn't everything have more than one use? There are spears people call bangsticks, which is just a stick with a shotgun bullet attached to it. You can use ammunition for anything like this, as long as you have something to break the the gunpowder with. Arrows can also be used as an actual weapon and not just to be lauched with a bow (c'mon man haven't you seen Lords of the Rings 2, Legolas can handle himself against people busting up in his grill).
Then again, these are just words to define what they are associated with. Would pistols be called ammo if you had a pistol launching cannon, or would bullets be called guns if they were used to direct and propel other objects?
I really don't think that arrows would break into a million pieces. Maybe if you had a hammer, but just shooting them into the ground or say, through someones abdomen wouldn't break them (maybe snaps it in half or cracks the tip). But yes, arrows would certainly be reused over and over again considering they're hard to make and very expensive. In fact, I've heard of whole battlefields being salveged, leaving the dead with nothing but their undergarmets (I'm sure these were taken too) so yes, arrows would definitely be taken out of the ground, from a dead soldier, and pulled out of people.