JDen-
According to what I have read, from current articles to statistical books, while each group who had a commemorative coin made in their honor thought their commemorative would sell all the authorized strikes, in actuality they did not. Many moderns went back to the melting rooms.
Modern commemoratives have been restricted to 500,000 strikes, but Treasury Secretary is allowed to increase the total number, which John Snow did for the U.S. Marine Commem. He increased the total number from 500,000 to 600,000.