There's a difference between using a brand-new Node.JS framework that's barely out of alpha and using Rails/Django/etc which whilst fairly new are proven to be stable and reliable, and are in use at big organisations.
So the business owner relies on the tech provider who hopefully isn't in a full on romance with the newest framework/language just because it's new.
Ruby (the language) and rails (the web-framework) are not the latest fads to come out. Rails hit 1.0 in 2005, a.k.a. almost 8 years ago, ruby is much older.
Although there can be good reasons to choose something new, I agree with your overall sentiment. But we seem to have extremely different views on what constitutes "new"(node might qualify :)