Not everyone has a 'nice Atmos quality audio system'.
I was all-in on 5.1 for DVD concerts, movies and DVD-A audio discs. Focal powered monitors, Sony LCOS 55" TV, then upgraded to LG OLED 65", which made me want to upgrade everything to 4K - my ATV receiver, Apple TV and BluRay/DVD player. It got pricey, but the upgrade was worth it visually.
When Atmos started happening I enjoyed the better Atmos releases folded-down to my 5.1 system, it certainly seemed and sounded 'good enough' to these old ears. I started buying physical Atmos media from SDE and other resellers, which usually also included a 5.1 surround mix in addition o Atmos and hi-res stereo. Still sounded good enough to me.
But being in the audio business, and hearing 7.1.4 and 9.1.6 Atmos releases at studios in LA and Nashville, coming back to my home to listen to them folded down wasn't good enough anymore. I added a pair of Focal Dome speakers as sides to go 7.1 - this made a BIG difference in the Atmos playback experience. And then it was even better than good enough.
BUT... it bugged me that I didn't have the .4 - what was I missing not having the height channels? This bugged me, so that 7.1 wasn't good enough any more. I didn't want to tear up my ceiling to install 4 speakers. A lot of folks here and on Steve Hoffman's forum said there wasn't much up there, mostly reverb and effects. But still, not bugged me,
So I poked around, got some advice from friends in the biz, and found some wedge monitors I could mount on the ceiling and run the wires along the corners or the walls and ceiling to hide them. Put all the measurements into the DAART software and installed the heights accordingly.
So now that I've got a Dolby-compliant 7.1.4 surround system in my media room, is it good enough? Yes - I do not feel the need to go to 9.1.4 or 9.1.6. I have not seen many Atmos mixes that take advantage of those extra channels, anyway. But I thought 5.1 folded-down Atmos was 'good enough'... until it wasn't.
Not all audiophiles will go to the trouble and expense to upgrade their home theatre/entertainment systems to 12 channels of playback. Fo those that do not, 5.1 fold-down Atmos is good enough... until it isn't ;-)