> where you gain flexibility and get the scaling for free.

Is it really for free? While I tend to agree with your point, one of the wrinkles here is that the older SQL systems have been beaten to death in production. We've had all sorts of 'little problems' with some of these newer systems. And this is not just about runtime issues, the 'hardened product' benefits reveal themselves in more secondary things like education, troubleshooting, monitoring, add-on products, and backup.