Probably because the AR/XR glasses are not yet at a stage where they could be used by the general populace.

I have Viture XR Pro, the edges are still blurry and even though glasses have a miopia adjustment it has been difficult for me to get a clear image, not to mention the issues of IPD. Having a display at arms length still has many advantages over the face mounted displays.

That being said, as someone who feels the need to wipe any and every speck of dust off the display, the glasses have resolved that issue, it's just that they get heavy and painful after just a few hours of use.

In my opinion, we're not there yet, but I'm very optimistic for the future.

Valve already failed with Steam Machines. There's not a compelling enough reason for them to split production of the Deck into two divergent streams with lesser economies of scale.

Also, 'just' the deck in a box still needs the same regulatory approval.