It’s faster and it increases productivity. There are quite a few big names that went the Node way because of this (netflix, uber, Paypal) and not just. You avoid the breach between frontend and back end development and move in a more unitary direction.
Dan Shaw, CTO and co-founder of NodeSource, a provider of support services for Node.js shops: “Node.js is rapidly replacing Java and .NET due to the agility of the Node.js software development lifecycle. Building a Java app typically takes six to 24 months from start to finish. In contrast, Node.js applications take two to six months.”
Tools, like npm and now Yarn, make working with Node.js a piece of cake. You get a consistent, reliable and fast workflow that changes development entirely.
Code reuse through prototyping and class inheritance. This is another point in the faster development column.
Real time apps compatibility. Node works very well for gaming apps, chats and others.
A modular construction allows you to change things easily in small particular modules which makes maintenance and future development almost headache-less.
On a separate note we would also list the Node.js Foundation as a bonus point for getting into Node.js development. Constant updates, with a clear calendar and a driven and united community are features that innovate and push development forward. Also, there are plenty of companies that use Node, we are testimony of that.