I didn't read every word of every post but I have a few thoughts:

1) Yes, airlines execs look at accounting. I don't know about airlines for sure, but after 35 years in insurance I KNOW insurance execs look at accounting.
2) Nobody on FT knows how airlines really look at things. It would be logical that the same companies that do "revenue management" to squeeze every dollar out of a revenue seat would do the same thing out of seats sold for points, but we don't know. We also don't know how many points go to FTers who extract every nickel of their value and how many go to low-frequency users who will use them inefficiently or let them expire unused.
3) Notwithstanding the T&C, state regulators will get in the act if the carriers go too far. I'm not positive about this, but here's my memory. FF programs started in the late 70's or early 80's. Award charts were much more generous then. In 1988, Eastern Airlines, strapped for cash, did a promo "Fly once in the first quarter, get triple miles all years." Everybody else matched that. So LOTS of miles were given out in 1988. By the early 90's airlines were starting to devalue, but the state Attorneys General pretty much got together and negotiated with them on how much they could devalue. I remember specifically that most of my miles were on United and I had a bucket of "old" miles that could be redeemed at the "old" (more generous) rates through a certain date, sometime in the late 90's.

Remember too that these are still marketing tools. What will a carrier do, increase all award requirements by a factor of 10 but then increase all future earnings by 10, so that you now get (say) 300,000 points for signing up for a credit card rather than 30? For all the whining about devaluations, the points are still certainly worth something, especially to FTers who optimize their value. Through various means and methods I have about 2.5 million miles saved, and while I'd be quite happy if I could get two first-class tickets to Australia for 120,000 points (which was the 1980's price on United, although honestly I think "first" then might have been what we call domestic "first" now), I can still use my points. They're hardly worthless.