It's simple. People who bought the headset with their own money, and are sharing the experience because it's cool (or not). Smaller yt channels which have no chance to strike a deal with hp (or any hardware manufacturers for that matter). Not a well known channel who just so happens to get the pre-production sample before anyone else. That sort of thing.
And if "we do not preorder" is good for games, then it's even better in the hardware world, where you pay huge sums of money for some yet unreleased product. Notable cases in point: first reverbs (recalled), first oled tvs very prone to burn-in and manufacturing defects, valve index knuckles, rtx cards which everyone expected to be a messiah and they provided only 30% performance over 1080Ti... As a fun fact I bought an OLED in 2017 and am now on fourth replacement matrix because of manufacturing defects.
As far as availability goes, yes, you're probably right. As for the price, I don't think so. And even then, the only thing you will miss is the early adopter hell, where your shiny new toy crashes and refuses to work because there are wrinkles in the software that need ironing out. Been there done that with HTC Vive, participated in the Pitool pimax hell of my backer friend, and also done that to the lesser extent with Valve Index which also needed an "incubation period" of about two to three months for the steamvr to "settle".
I also have two particular requirements when it comes to VR, namely clarity (the field of view which remains clear when you look with your eyes off the center of the lens), and controller comfort. Knuckles set a new bar in controller comfort, and WMR controllers are as primitive as Vive wands in this regard. No touch-sensitive surfaces as well. Reverb might have good clarity from what I have heard so far, but as for me, that's untrustworthy sources.
.
