Part of me does think that its the bike industries way of selling something new, but the other part of me realizes that if there was a demand for short travel/hardtail 26inch bikes more companies would keep making them.
BW -- I think the demand for hardtail/short travel bikes has shrunk because of the overall performance improvements in rear suspension designs. When we were shopping for our bikes, which was as recent as 3 years ago, there were still a lot of drawbacks to rear suspension, and these were a significant disincentive to buying one. Loss of power, poor acceleration; poor climbing ability; vague disconnected "trail feel"; much heavier weight; more maintenance; big price differential....all of these combined, when viewed next to a good hardtail in the eyes of buyers such as us (ie. located in an area where the trails were fairly smooth and easily rideable on a hardtail by a skilled pilot), it was a no-brainer. The lighter, faster, cheaper, better spec'd hardtail won hands down. And if you asked my wife today if she would trade in her little 26" hardtail XC race bike for a full-suspension rig, she would laugh and say "No way, Jose!".
These days it's a different story, however. Prices are lower for rear susp. bikes, rear triangle designs have more or less eliminated the performance drains, the bikes are lighter, and the other components are not being scrimped on. A rider like my wife may actually consider one if she took a really good model for a test ride. OTOH, if she got on a quick, agile, light 650B hardtail, I'll bet she'd fall in love.
So, if asked to replace her bike today, she would probably say no, and that she will wait a few years until the the 650B thing matures, and then look for a top-notch fast hardtail. Makes perfect sense to me.
As for the bike industry trying to sell a particular design just because it's "new and better", well, I'm a bit cynical about that. There is something to that statement. A lot of people I talk to, including shop owners, are looking at all the new stuff with a raised eyebrow, and are frankly getting sick of it and are turned off by it all. Every year there are different standards for bottom brackets, drivetrains, wheel sizes, headsets....and on and on..... All of them claim to be better. No one is sure why we need some of it. I think a lot of people are savvy to this, and will pick and choose the technology that really makes sense and is a true improvement, rather than the latest fad. This may all backfire on the bike industry....we will see. There will always be those insecure people who simply must have the newest and best, and will probably go broke trying to live to that standard. But for the rest of us who just want to buy a great bike every 5 or 8 years, are willing to spend a not-insubstantial amount to get one, and then forget the technology and just have fun riding it, it's all more marketing babble and something that is best ignored until it's time for a new rig.
I suppose the latter attitude comes with age and maturity. I know a couple of guys in their late 50's and early 60's who live on the west coast (friends of my father-in-law) who still ride multi-day long distance endurance mountain bike races across the Rocky Mountains in the interior of British Columbia (starting in Whistler, and going inland from there). They each have five or six mtn. and road bikes in their stable, including some very expensive carbon full-suspension rigs, and have owned dozens of bikes in their lifetime. These guys are tough, experienced, expert riders, who were riding mtn. bikes when I was still in puberty, and you were probably not even born yet. Well, I asked them what their favourite bikes where. The younger guy pointed to a ten year old Kona scandium hard tail (Explosif, I think, white in colour) that had taken a good beating over it's life but was still going strong. The other guy singled out a Marin hardtail, also scandium or maybe Ti (can't recall), about 5 to 7 years old. The values they placed above all else were not speed (as in the fastest course times) or light weight or comfort; but rather agility and handling, quickness and acceleration, toughness, reliability and simplicity. Basically they valued a fun bike that was simple to maintain and could take a beating. They weren't wowed by full suspension or even 29ers. But they can make these simple bikes do amazing things, and ride trails on them that I will never have the nerve to tackle in my lifetime. As I said before, it's more about the skill of the rider, and less about the hardware.
Oh, and I asked them about tubeless. They just laughed and said they couldn't be bothered. Tried it; not worth the fuss for the marginal performance gains. But they do value good tires with rugged tread and lots of sticky grip -- Nevegal (most popular tire by far in those parts), Ardent, Fire XC Pro....that sort of thing; or Ikon for smooth trails.