For me the question isn't so much why do I choose Node.js and Javascript over other languages, it's why do I choose NPM over other module libraries. I think the ergonomics of the libraries and command line tools we use have a much bigger impact on our coding experience than the language itself.

And what I like about NPM is that there are a LOT of single file modules with a narrow, well defined scope. There are exceptions to this, like Ember or Angular, where they try to package up everything you might need. But there are also smaller frameworks like Vue.js and even smaller packages still, which do a single aspect of data binding or rendering or whatever.

And it's those granular little packages where I think the NPM community ends up exploring just about every possible way to do get something done, and often comes up with a new idea that can teach me something.

The organizational and software complexity behind an interface like Rails or iOS or Ember I think discourages app developers from questioning the interfaces they are using, and participating in shaping the landscape under them. I think that's a shame. The NPM community does it better.