Frameworks are making the whole JS thing much easier now, and since you have JS in the browser, on every device on the planet, it makes a lot of sense to use node.js on the backend as well for certain tasks.

In 2014~2015, I can't imagine creating a web based backend system (or even a mobile app for that matter) in anything other than JS. The costs of hiring a C++/Java/Ruby engineer are not so easy to justify. Beyond the monthly costs, it's also the amount of time it takes to create a powerful, reactive web interface.