It's incredible to me that people are so skeptical that they think that a company releases something that requires a different standard solely as a way to stimulate sales. You know the best way to maintain/increase sales? Make the best product. And most of the time, when a new standard is introduced, it's because it represents a step forward, not a convenient way to sell more wheels or forks.
Every time something new comes out, the skeptics run rampant, and that is a good thing in reasonable doses - Rapid Rise is a good example of something that the market voted NO on, even though some folks at Shimano will still claim it had something going for it, in the face of overwhelming pressure not to sell it anymore. But if new standards weren't championed by companies with the balls to do it, we wouldn't have things we take for granted now, like (irony alert!) 20 mm axles, or disc brakes, 1.5" steerers (let alone 1.5 / 1 1/8 tapered steerers), tubeless systems…do I need to go on? All of these things drew the same kind of ire - and all of these things are now embraced in the market segments they were intended for.
Not every piece of technology is for you, but the companies putting it out there aren't saying it is either. 15mm is not intended for use on the North Shore trails. People will do it, but that wasn't why it was designed. 15mm forks are not replacing ones with 9mm (for now), they're offered as alternatives. Bike companies spec them where they make the most sense but the aftermarket consumer still has a choice.
You cannot compare one 15mm fork to one 9mm fork on a completely different bike, judge it to be a noodle and condemn the standard - that is absurd. Front end stiffness is subjective, and it also depends on the system as well as a lot of other factors. Fork, bar, head tube, stanchions, bushing overlap - stiffness comes from all of these components. The axle is a big part of it but you can only compare the same fork on the same bike with two different axles to get an accurate idea.
The 15mm standard was co-developed by Fox and Shimano - SRAM's two strongest competitors. Obviously they won't just switch over to it immediately - they'll continue to defend the status quo while they decide for themselves. In the end, whether they switched for the simple sake of sales they might lose or because they changed their mind about the benefits of 15mm, who really cares? The consumer wins because now all the suspension co's are using that standard. You can bury your head in the sand and stick with 9mm if you want - the option still exists!
Take a deep breath, back up and take a look at it, and be a bit realistic. In the end, bikes are SO much better now than they were even 5 years ago, and it's these things that SEEM insignificant like axle width or 20g saved here and there that all add up to make it that way.