That's not true on NUMA systems with multiple CPU sockets. You should have at least one thread per NUMA region for optimal results. Critical for example for running multiple 40 or 100 Gbit ethernet adapters.

Then again, you probably aren't going to run Node.js on those systems, at least not for handling heavy I/O.

the world doesn't revolve around making HTTP servers. Maybe you aren't writing apps that do parallelizable serial computations but please don't generalize.

Backend and file systems, network and systems middleware do not need the abstraction model and overhead of a language designed to add dynamic content to fucking WEBPAGES because it can and it seems easy.

Well, file systems nobody writes in JS, so that's irrelevant.

As for "network and systems middleware" depending on what it does it can be a great fit for JS and especially Node, which is a lightweight logic layer on top of libuv.

'Lightweight logic layer on top of libuv': well if I can design, predicate and tout my language on 'event' orientation but then when it needs to do something else it becomes a thin logic layer over the hosts threading model: that's just a win!