Are Europe's fields filled to the brim with millions of casings? Or have they all been collected and recycled? What about the contemporary wars in Afghanistan and Iraq all the millions of spent shells just left in houses and streets?
It must add up to a fair amount of money if you were to recycle them all! Or is the value negligible?
What about the shells of artillery pieces? Are they just left?
Has there ever been a battle where a nation strapped for resources has made a point of collecting every shell casing?
Brass is a relatively valuable material, especially in such huge quantities.