I've seen some good commentary here. At least from my POV, there are a few arguments to be had in response to comments in here:
(1) There will always be open seats to fill somewhere. Nobody running regular service on a route is ever going to quite get to 100% load factors in all classes of seating on all flights, for the simple fact that demand does not shake out that smoothly and supply on any given route comes in substantial chunks (those chunks being the size of one's smallest available plane for that route). The question is how many open seats you tolerate, how many you fill with reward travel, etc.

(2) There is a tendency in most industries of a "herd mentality" since if everyone screws up, nobody screws up. The result is that identical mistakes are copied and pasted into many companies...and I think we've seen the FF side of things engage in this just like almost any other industry.

(3) Modest devaluations, on a regular basis, are to be expected due to ticket price inflation so long as reward "prices" (in terms of points needed for a given redemption) aren't actually pegged to ticket prices. If a given ticket is available for 25,000 points this year and next year the cash price goes up by 5%, in theory the price for that award should be 26,250 points. However, this does not happen and you get "sticky" devaluations that tend to be a lot more chaotic. Between rising load factors and rising prices, this probably resulted in a lot of points being booked at a given price but redeemed at a far higher price.

(4) Credit cards as the problem for the programs as they exist now. With some FF programs, a bit of aggressive CC application management can spit out 100,000 points or more basically overnight, depending on the offer du jour combos out there. This is a major problem for a whole host of reasons, not the least being the ability to churn offers every few years (particularly if an airline switches companies) and pile up a ton of points without flying much (if at all). If points are then being cashed in at relatively "good" values for the customer (this varies from line to line), a major problem emerges as points flood onto the market. If we're going to see some sort of long-term stabilization in values, some of this has to be reined in (possibly by airlines capping off bonuses or limiting the bonus to "once per FF account, full stop"; possibly by airlines requiring the issuing bank to limit sign-up bonuses; possibly by hiking the sale price of points used for various bonuses; and possibly by another effort).

(4a) It is entirely possible that there are additional mechanisms at play beneath the surface of some programs w.r.t. credit card offers. I would not be at all surprised if the airline gets some sort of bonus/kickback for signing people up for their cards from the issuer (i.e. a bank offering the airline another $100 per card "sold" in addition to the $400 the airline would get from the point sale). Remember, the bank/card issuer wants the card to get used and wants fees from that. The airline wants a mix of cash, bodies in seats that would otherwise go vacant while discharging a liability, and ideally some level of increased customer loyalty.

(4b) With some partner offers, the same as 4a applies. Hertz, Enterprise, etc. likely want to maximize repeat business at their airport terminals...so it is quite possible that they're willing to pay a (modest) premium for their relationships with various airlines.

(5) As noted, there are several different "markets" for each airline's FFP. The family that wants to be able to get free tickets to Orlando is not the same market as the executive who wants to be able to bump to Trans-Atlantic FC for free...and neither of these are the same as the FT user who makes all of their miles through churning.

(6) On Southwest in particular: I think it is quite possible that Southwest made a goofy mistake (possibly as stupid as someone flipping an equation in a contract calculation) or got too clever by half. It would not be the first time in the industry that something like that had happened, let alone other industries.

(7) As to the possibility of floating an FF program as a separate entity...the issue there is a mess:
-One issue is that any profitability from the program (assuming it was profitable) would be lost from the airline(s) in question. If an airline got desperate, this might be a Hail Mary lacking grace, but I suspect they'd rather keep the program in-house.
-Another issue is the fact that if a program is somehow "actually" losing money, the implosion would be epic.
-Yet another issue is the fact that as soon as the airline sells the program, the airline loses control of the miles/points that are in the program. Not only that, but they lose control of the program itself. This presents a couple of traps, but one could be that an airline goes through some sort of major overhaul...and the program proceeds to stop doing business with the airline. If an airline devalues points internally, that's not a problem. If an airline were to try and devalue awards available to an external company it had spun off (and that materially affected the results of the spun-off company) there's a good chance that somebody would be suing somebody (possibly even the FFP suing the airline...which would be all sorts of interesting to watch).
--Another is a merger disaster of epic proportions...

For a hypothetical scenario, let's assume that USAir had floated Dividend Miles before the merger with AA, so you get Dividend Miles plc. Ok, now we have two programs in one company (AAdvantage and Dividend Miles need to come together somehow). Three scenarios could play out:
(1) Dividend Miles plc buys out AAdvantage as part of the merger. Probably the cleanest solution available, with the programs merging outside of the airline.
(2) American throws Dividend Miles plc out of the airline in lieu of AAdvantage. Cue lawsuits, but the merged entity could just choose to try and force a cash payoff of the "dispreferred" program.
(3) Both programs persist in the company. Cue a bidding war as both have some claim to operate. Great for members in the short term, likely a complete disaster in the long term.
(4) Dividend Miles plc decides it wants nothing to do with the new company and uses the merger to break loose. Ok, let's ask ourselves a question: What would happen if the merger was going on, things sour between the merged entity and the FFP, and someone else poached the program writ large? i.e. What is to prevent Delta from buying out Dividend Miles plc to grab the traveler data and then carrying out a brutal devaluation (or even just paying out to members and killing the program)? What is to stop a foreign carrier from buying a domestic FFP as a means to "back-door" their way into the US market?

Now, obviously all sorts of legal covenants come into play and the lawyers would have a field day with all of this...but it is entirely possible to see an airline's FFP get cross-ways of it in all sorts of interesting ways, especially when one inevitably decides it would be profitable to try and screw the other somehow.