ATMOS, just like additional surround rear speakers, is like accessories for your toys.
It's more about trying "new" things.
If you are a publication or an Audio dealer, you might feel "obligated" to keep up with new formats.
I think for 99% of all people who have rooms smaller than 25', a 5.1.2 ATMOS setup is good. More doesn't hurt.
The Salient speakers will always be the MAIN front 3 speakers and subwoofers. The surround speakers (including ceiling ATMOS speakers) are there to enhance the experience.
So a good 5.1 (especially w/ multiple subwoofers) system is great.
ATMOS, ONLY if done correctly with ceiling speakers, might give you a little more additional enhancement.