I expect most people use at most a soundbar. Which, regardless of what it advertises, is really just 2-3 channels and maybe a subwoofer.

And the rise of phones means there's a lot of stereo or even mono.

Bought a receiver years back, only ever bought two speakers - whole thing isn't plugged in since I moved two years ago, just the little speaker in the TV with no bass.

My guess is a lot of people with bigger TVs are getting soundbars. They are easy to setup and doesn't require wires. I won't switch from 5.1 setup but if I ever move I would give it a try. Built-in speakers I've used in hotels/airbnbs are not great.

Soundbar marketing has a lot of snake oil about bouncing soundwaves around a room to simulate 13 discrete speakers or something. I've got no science, but I do have some serious doubt whether the bouncing stuff works at all. In my imagination, soundbars are basically stereo, or maybe 2.1

I've always considered them the "Bose" of our generation (built on shitty engineering) - they sound better and bassy and so they sound "good enough".

I was skeptical for a while. But I have a friend who is used to a 5.1 setup and moved to a much smaller apartment. He has switched to a soundbar with Atmos and says it is on par. The fact that he "downloads" Dolby Atmos versions of movies even when they are available for streaming added some weight to his opinion. I still did not compare myself so would not go to fight over this.

I don't know your friend, but people are not good at listening. There's a whole industry catering to audiophiles with products that can't pass a blind test. Cynically, I might suspect that your friend is trying to justify their purchase to themselves. Or maybe I'm wrong. But the anecdote doesn't convince me either way.

Just wait a few years and you'll be like me, seven speakers and one good ear.