How can you not have multichannel system

The question I asked remains unanswered; what listening perspective do you get with multi-channel playback? As stated before, it makes perfect sense for recordings made at a live concert where listeners are surrounded by crowd noise. But what is gained by using rear speakers for a studio recording? Is the listener sitting in the middle of the players? Mig007, you mentioned "Blood On The Tracks," and I am seriously curious as to what is presented in the rear channels.
I understand the analogy of getting higher resolution with SACD but disagree that that would be enhanced with more speakers. In fact I think it would be more difficult to discern different instruments unless they are specifically mixed to emanate from one speaker. That would sound strange.
My system for "serious" listening is in a small room which is not conducive to having rear speakers so stereo is where I'll stay but I'm curious as to what perspective the listener is in.
Understandable for video, which I have zero interest in, but I don't see it for audio. I don't doubt that good multi-channel system with a well engineered recording can sound wonderful but I know a good resolving stereo system, setup in a properly treated room, can present sonic nirvana.

Tvad...A few decades ago I messed around with various forms of "derived" multichannel, including some circuitry of my own design. In general I agree with you that the typical stereo recording doesn't work well in full surround.

However, some particular recordings do work very well. Few recordings are made with just two mics. There is usually an ambience mic at the back of the hall, and when its signal is mixed in out-of-phase between the two channels it will, upon playback, emerge from the rear, exactly where it belongs. One Judy Collins cut, "Amazing Grace" is exceptional. She sings in a church, at first solo, but then the congregation comes in all around you. At the end, as the sound decays you can hear people behind you putting their Hymnals back into the wooden racks! Spooky!

But usually four channels from two is overreach. However, three from two (center) always works well. I play stereo material that way on my multichannel system. I have used a center channel for about forty years using various ways to derive it.

Now, for true multichannel, I have some recordings of classical chamber music where each channel has one instrument isolated in it. When you play back such a recording you are not "transported" to the studio, but rather the performers are transported to your listing room. The realism is amazing.

I have been a part of many string quartets, and have never heard that. I remember in the early days of stereo, I had a recording of a ping pong ball bouncing left and right. This is even worse.