There seems to be somewhat of an upswing lately though. Federation is cool again, and many of the implementations active now seem much more stable, instead of weird half-research projects that killed themselves by ignoring the real world too much (which was sometimes true to their goals, which is fine but unfortunate).
Who would advance it? Can you even get multiple parties to agree on what's in it? Is there any identity required? What's there to stop this being another "Bluejacking" vector but now with dick pics?
Given all of the above the proprietary route seems inevitable, even for protocols over Bluetooth.
AFAIK, they changed policy a few years ago, so that even if you set discoverability to "everybody", it changes back to "contacts only" after a few minutes.