Hipster hubris? The "cool kids" crowd that jumped from PHP to RoR to node.js.
Please don't follow the hype: many of this tools will be abandoned when a new framework/language comes out and this will leave the Unix userspace more fragmented.
Maybe it's just that that's the tooling/language that the author knows. I've been guilty of writing a tool in the language I'm most familiar with whether the greater community thought it was a good idea or not.