I’ve spent time in some of the largest distributed computing deployments and cost was always a constant factor we had to account for. The easiest promos were always “I saved X hundred million” because it was hard to argue against saving money. And these happened way more than you would guess.
Yeah obviously if you run hundreds or thousands of severs then efficiency matters a lot, but then there isn't really the option to use a single machine with a lot of RAM instead, is there?
I'm talking about the typical BigCorp whose core business is something else than IT, like insurance, construction, mining, retail, whatever. Saving a single AKS cluster just doesn't move the needle.
I think my original point was more in the “engineers want to do cool, scalable stuff” realm - and so any solution has to support scaling out to the n’th degree.
Organisational factors pull a whole new dimension into this.