Well, I don't know a lot about it, but I would assume they had the major power floor to PREVENT 9mm from becoming a major caliber.
Plus, there were all sorts of other calibers, like 9x21, 9x25, 10mm, and the .40 and glock pistol came out in timeframe that was most unfortunate for Mr. Clark.
Didn't they actually introduce a bore size limitation as well??