Norman,
Unlike the tendencies of US and allied forces, in Germany carrying a sidearm was not a symbol of rank. Pistols (not just Lugers) were issued to anyone whose duties made it impractical to carry or use a long arm on a regular basis.
This would have included bicycle or motorcycle couriers, artillery support personnel, ambulancers, supply train personnel, headqurters staff, Engineers, telegraph personnel, mounted cavalry, railway personnel, observation balloon personnel, civilian workers near combat or sensitive areas...the list goes on and on. You begin to get the idea that the Germans were very practical about pistol issue.
If you can track it down, Volume IV of
German Pistols and Holsters 1834/1945 by Robert Whittington details the issuance and use of pistols in WWII by the German army tables of organization. Here is the link to a review on Jan Still's Forum which goes into a bit of detail:
http://luger.gunboards.com/topic.asp?TOPIC_ID=117
--Dwight