Good question. I recently had my ceiling torn apart to add recessed lighting and thought about adding atmos before I bought my 975.
I have a 5 channel amp ()7500) so here it was:

Marantz processer with Atmos at the time: $1200
Two Monoblocks to match my 7500: $700
Two used MK inwall speakers (I'd install in ceiling):$300
That's $2200.

The cost of adding three zones of recessed LED lighting with gimbels on dimmers was $2700 including repair work. To add $2200 more would have had me doing some fancy explaining to the wife!

Then I started thinking about the impact it would have on my system and what that money can go towards. Was thinking my 10 year old pair of Subs might be due for an upgrade soon enough and a pair of JL E class run me about $3000 and impact far greater than a few overhead rain effects or helicopter blade from above.

This product is perfect for my situation because I have all the other bells and whistles imbedded in my system and it gives me a great pure processor and that's all im paying for!!!! I came from a 990 and it served me well. I wanted to simplify my system to HDMI and make it easier for others than myself to use it. More important, it sounds better than my 990!!!! This was a very easy Choice. Since I had to take everything apart before the work was done, it was the perfect time to do this upgrade!!

Atmos won't do anything for the music and there is a limited catalog of movies. I also still use Netflix to get my bluerays rented and they don't ship out Atmos coded discs.
I don't buy movies either. At $575 for the 975, im paying for what matters now and getting great performance at a very reasonable price. If I was paying $2000 for a receiver, or building out a dedicated home theatre, I would for sure make sure it was included.
That's my thought process.