Canned soup never used to have expiry dates. Now every can seems to have a "best before" date. Do you believe that expiry dates on canned soup are...
Necessary, because it can help prevent people from eating soup that's gone bad, OR
Unessessary. In fact, it's just a way for the soup makers to get you to throw out perfectly good soup and buy more.
ETA: Hmmm.. Funny how I seem to be able to spell "necessary" but not "unnecessary"... :)