Dave just pointed me to Truckin', by the Grateful Dead, on YouTube, the world's personal jukebox. So I'm listening on my little foldable Sennheiser PX-100ii headphones, picking out the voices and instruments. Vocals and bass are in the middle, throbbing out of my pituitary gland. The drum, mostly snares, is a bit to the right. The organ is a bit to the left, and guitars are at the far left and far right, next to my eardrums.
On speakers this produces a "sound stage" meant to replicate what the band would sound like if it were right in front of you. In your head it's just... interesting.
Stereophonic sound was not meant in the first place for headphones. It was meant for living rooms and other rectangular spaces where listeners could sit facing a pair of speakers near an opposite wall, all positioned to give the sense of performers being right there, arranged in order, left to right. Perfect similitude wasn't possible, but it was at least an ideal. Subsequent approaches (quadraphonic, surround sound) served the same purpose. So do those external speakers you can get for a home computer screen, usually with a bass unit somewhere and little treble speakers to flank the screen.
But now more listening happens with headphones than with speakers, and speakers are used more typically just to put the same sound in different rooms, or in parts of the same room (such as in restaurants), or in outdoor locations. These don't need to be stereo, and in more and more cases are mono speakers connected over wi-fi. That's what Bose and Sonos are pushing these days.
Meanwhile, surround sound (e.g. 5.1) is the default ideal for your entertainment room. What's left of plain old stereo is what you can't help getting with your mobile earbuds and headphones. Because you only have two ears. (Note: binaural recording will give you a nice you-are-there experience, though.)
It's also interesting to me that video recording on mobile devices is up to 4K now, yet sound recording defaults to mono, which could hardly be more retro. (Do any smartphones or pads record in stereo through the headphone, USB or Lightning ports? I don't know. I do know it's not a priority for manufacturers.)
Anyway, bottom line: stereo isn't really dead. It just lives mostly in your head.
Bonus link: Searls Glasses. Better than Google's, 'cuz they have 3-d cameras, record in binaural sound, send and receive privacy preferences, and have a design in the public domain. Their only disadvantage is that they don't exist. Yet. Feel free. You're welcome.