For the uninitiated 3DoF means the headset only tracks the rotation of your head, not your heads absolute position as you move around, while 6DoF tracking does both. 6DoF is also much harder to implement.
Besides, VR is already cheap. A new Quest 3S is just $300 and can do pretty much all of what the $3500 Vision Pro can do (just worse); if you just want VR games you can get used 6DOF-capable PCVR or PSVR headsets on eBay for closer to $100.
Besides 'it's Meta' ; what is it doing with my privacy? I mean actually proven things, not 'probably it is'.
(I am not saying it isn't, but I haven't heard anything in this regard, so it would be interesting to know)
I'd like to place a picture with a QR code in it, have somebody scan the code, then have the option of jumping into a world.
Apps can't access the cameras so you can't write a QR scanner. The Quest has a decent web browser but you can't access the cameras and make a web based QR scanner.
Without access to the cameras apps cannot at all understand the environment and enable you to interact with it. AR apps now have a special module that identifies a physical volume inside your space on a session by session but that's a pale shadow of the SLAM tracking of the Microsoft Hololens and Apple Vision that let you stick a "hologram" into the corner of your office and have it stay there.
Quest 3 devs need more access to make more interesting apps.
I think of this kinda like the data collection with many phone apps. I understand that it needs access to the networks to make connection to wifi or bluetooth, but why is this bundled together with an app's ability to record and send that data back to the developer? There has to be a better way to handle all this.