Why didn't other nations have a shotgun in their infantry arsenal?

A question I’m hoping will make it to Out of the Foxholes: Out of all the major nations of WWII, it seems that only the Americans made regular use of a shotgun (the Model 1897 Trench Gun). Was there a particular reason why hardly any other nation made use of a pump action shotgun for their army during the war? I was also told of a rumor that the Germans considered this trench shotgun a war crime during the First World War.