As far as the design question, there are many courses that will never get a tour event nor do they have any interest but the membership spends money to increase length because they are slipping in the rating.
When you look at the majority of new courses they designed longer to attract the attention of golf digests best new list. Very few people set out to create a great 6,700 yard course anymore, length attracts attention on lists.
Do you really believe that? Maybe my area of the country is different, but the majority of courses I've seen built in the last 20 years near me are under 7000 yards from the back tees. I can also think of PLENTY of heralded, list-making courses from the last 20 years that are under 7000 yards as well, as I'm sure most of the guys on this site can.
If anything, the courses on the lists that have stretched their back tees have done so because they have the means to do so and they continue to remain relevant and attract strong players and, in some cases, higher level tournaments. Can you name examples of courses that were slipping in the rankings, added new back tees, and immediately climbed back up? Do you believe that Cypress Point is doomed to start falling out of its lofty spot in the near future?
I think it must depend greatly on the area. I'm sure I missed some, but here's a list of notable courses in Arizona that have opened up over the past 15 years ...
Aguila Golf Course, 1999 (Gary Panks) - 7076
Blackstone, 2005 (Jim Engh) - 7089
Coldwater, 2000 (Forrest Richardson) - 6758
Copper Canyon, 2007 (Schmidt/Curley) - 6845
The Duke at Rancho Eldorado, 2003 (David Druzisky) - 7011
Golf Club at Estrella, 1999 (Jack Nicklaus II) - 7139
Gallery Golf Club (South), 2003 (Fought/Lehman) - 7468
Papago Golf Course, 1963/2008 renovation (William Bell/Billy Fuller) - 7333 (I believe it was previously just shy of 7000)
Poston Butte, 2007 (Gary Panks) - 7282
Quintero, 2000 (Rees Jones) - 7208
Raven Golf Club at Verrado, 2004 (Fought/Lehman) - 7258
Southern Dunes, 2002 (Brian Curley) - 7517
Sundance, 2003 (Greg Nash) - 6944
Trilogy at Vistancia, 2004 (Gary Panks) - 7259
Vista Verde, 2006 (Ken Kavanaugh) - 7229
WeKoPa (Saguaro), 2008 (Coore/Crenshaw) - 6966
Almost everything is over 7000 yards, even community (even retirement community!) courses that will never express any interest in hosting a tournament. Heck, I didn't even mention Dove Mountain which is somewhere in the neighborhood of 7800.
Sure, it's the desert, the ball probably goes a bit farther, but ... whew, that's still a lot of 7200+ yard golf courses. That's a lot of golf course for anyone, anywhere.