Why don't they record in ‘surround stereo’?

Interesting taken from Wiki" 

Stereophonic sound, or more commonly stereo, is a method of sound reproduction that recreates a multi-directional, 3-dimensional audible perspective. This is usually achieved by using two independent audio channels through a configuration of two loudspeakers (or stereo headphones) in such a way as to create the impression of sound heard from various directions, as in natural hearing.

Because the multi-dimensional perspective is the crucial aspect, the term stereophonic also applies to systems with more than two channels or speakers such as quadraphonic and surround sound. Binaural sound systems are also stereophonic.

Fascinating comments above. I guess another huge obstacle is all the Cable connections would have to be increased coming out of the back of the components if you expand from two channel listening to more channels. Vastly complicating the cabling and connectivity issues of the components.

If you have a good speaker system and great amplification, I guess the benefits are marginal. But there did seem to be openness in comments that there is potential it could be actually better.
 

Because I have nice speakers and amplification, including lots of tubes, I tend to listen to my home theater with two main speakers, eliminate the center channel and leave in the surround rear speakers . Often times this is a lot better. But other times you need the center speaker so the dialogue is more discernible and doesn't disrupt what's going on in the main speakers. This configuration can be handled toggling back-and-forth between two settings settings on the home theater remote. Ie. Super easy to go back-and-forth.

So at least on the home theater side I have the flexibility and it is working out really well

Try 5.1 SACDs.

Besides your AVR can send matrixed channels to the rears so what's your malfunction?

For a, moment I thought kota1 was back.

There are now hundreds of Dolby Atmos remixes of classic stereo recordings. It’s not generally understood that Atmos is a superset of Dolby Digital 5.1, and Atmos content will be automatically down mixed with no loss of fidelity to 5.1 if the AVR does not support Atmos.

My setup is: AppleTV 4K -> HDMI -> Marantz AV8003 pre/pro -> Marantz MM8003 power amp -> 5.1 speakers. This receiver dates back to 2010, long before Atmos, but the AppleTV automatically sends discrete, uncompressed 5.1 channel PCM to the AVR. Sure enough, the Atmos mixes play back perfectly in 5.1 surround, and are quite different than the 2-channel mixes. And there are hundreds of titles in Apple Music in Atmos format ... some new, some going back to the late Sixties, like The Doors.

True, the quality of the mixes vary, as it always has for surround sound. Some are very much better than the stereo release, and others are gimmicky and not very good. But most are an improvement on the stereo version, which are only a few clicks away if you prefer that.

Apple Music lets you choose tracks in several formats: 44.1/16 CD resolution in stereo, 96/24 resolution in stereo, and Dolby Atmos, which appears on the faceplate of the receiver as 5.1 PCM Discrete (not Dolby Digital). Based on the display, it is the AppleTV, not the receiver, that is decoding the Atmos stream and converting it to uncompressed PCM streams.