Let's look at it this way. If AA were to give all 16 F seats in the current configuration as upgrades to AAdvantage elites, that is still 16 seats in Y that get sold, above the actual seat count.
I'm curious as to who actually buys first class tickets. Most people I know who fly for business can't buy a domestic F ticket on a corporate expense account. People I know tell me that they can only book a premium cabin for travel to Europe, Asia, and some parts of South America.
Here's some irony to think about. Back in the 1990s, the MD-80s often had 12 seats in F. Then, they were standardized at 14, before eventually getting 16 seats. Meanwhile, the 737s were originally delivered with 20 seats in F. Then, when AA started to put some seats back while scaling back MRTC, AA went to 16 F, maintaining MRTC even though 2 rows of Y were added.
Lots of us buy first. Airlines have brought fares down out of the stratosphere and I think DL said 51% FC sell and by 2018 they expect 80%
Last fall, my wife and a friend of hers flew ORD-SFO-ORD on AA. The fare for F was around $825. We were looking to fly ORD-SNA-ORD this summer. Fares were north or $1050, to as high as $1500. The fares were even worse for SAN and LAX.
We would up buying OW tickets and using miles (PlanAAhead) for the other direction.
The reason I asked who buys F is because businesses have become stingier and stingier with air travel, as well as allowing employees to fly in a premium cabin. When my wife first started working what was then Cincinnati Bell (now Convergys) in 1991, you could book F for ORD to the west coast. Over time, it got to be that only people in Cincinnati or east could fly to the West Coast in F. Then it got to be that it had to be coast-to-coast for F. By the time my wife left in 2006, there was no domestic F travel, except for Alaska and Hawaii. At the same time, the number of hours increased for travel to Europe, South America, and Asia, to be able to buy F tickets, rather than J.
My wife's current employer, as well as friends of mine at various Fortune 500 companies, have strict limits on travel. It often takes 2 or 3 layers of supervisors to approve travel. With that kind of restrictions, about the only way people get into F is via the upgrade because of F/F status