Another use case: if you are a gamer, then rear surrounds would be equally as important as side surrounds to ensure a uniform sound quality for all 360 degrees. For gaming, you'd benefit far more from a 7.1.0 than a 5.1.2. Atmos isn't a factor in gaming yet, except for a few Xbox One titles.
AVR: Denon X4400H 7.1.4; 80% gaming, 20% movies, <1% music
Speakers: Klipsch RP-450C; L/R Klipsch RP-250F; Side & Rear: Klipsch R-51M; Height: JBL 2.5" satellites; SVS PC-4000;
Platform: Xbox One X on LG E8 55" OLED
Room from hell: 16x16x18' open loft, thin walls, hard surfaces, lots of street noise