To address your point rather than your sarcasm: headphones are unsafe while cycling because they block environmental sounds (though it’s true that music from a speaker can impact attentional blindness. There is also the shared experience of listening to music with another person. The ability to create a “music bubble” around you without disturbing others satisfies both parties.
Ultrasonic speakers aren’t even exotic tech. I first encountered one in a museum at least ten or fifteen years ago.
(Am fairly certain they aren't great if you are going for audiophile level reproduction - but from a safety perspective, they let you hear your environment - note, I have personally never tried them)
Quality isn't amazing, but it's acceptable and it isn't like you'd be enjoying a high quality audio experience with wind rushing past your ears using normal headphones, anyway.
Also beats getting hit by a car that you didn't hear.
I'm a runner not a cyclist, but I use AfterShokz headphones. The sound quality is suprisingly good, more than adequate for listening to music and podcasts when out :)
For personal safety though, they win hands down. I can hear cars and people easily and I'm much more aware of surroundings. Downside is though that if you are running down a busy road, the sound of cars can override the sound of your audio but for me, that's an acceptable trade off.
I have aftershokz aeropex. If you are hoping for studio monitors you're going to be disappointed. If you just want to listen to podcasts or "workout music" then I think they are great. I use mine way more often around the house than I expected that I would.
Ultrasonic speakers aren’t even exotic tech. I first encountered one in a museum at least ten or fifteen years ago.