Bob,
In 1958 the majority of golf courses in the US were of the 9 hole variety. A Green Section report from the period stated that there were an estimated 5,745 golf courses in the US, 3,308 of which were 9-holers and 2,437 were 18. If a majority can be considered 'the norm', you'd have to say that 9s were it, at least 5 1/2 decades ago.
The same report also stated that about 10% of all new construction was in golf/real estate developments, and given the economics of 9s and 18s it was almost a sure bet that the tables would be turned in favor of 18s in the upcoming decades.
Those tables have a good chance of turning once again, given all the constraints placed on modern-day golf, and it's very possible we'll see more 9s being built (or carved out of failing 18s), along with 6s, or 12s, or perhaps some 3s, in the future. 'The norm' has changed in the past, and if a wider vision of normal is to be achieved it will require people with foresight and funds. The whole process of change would get a shot in the arm if the present GHIN system were modified to accept scores from any number of holes.