Why we love Rails
Rails was the first non-enterprise, opinionated, complete Web framework. It had built-in pluralization of nouns! Database migrations! Distinct runtime environments! A huge bag of helper methods that abstracts common tasks and makes code read beautifully.
We still use Rails because it solves its specific problem the best, thanks to the years of development over other systems. Django is the closest competitor, but it has historically lacked the people-power that the Rails ecosystem had. For secure, stable, boring, simple CRUD: Rails. For most of the Web: Rails.
A wonderful community
Once we got into Rails it became clear that there was a great open source community around Ruby and Rails which made doing new or even scary things a lot simpler. There were great learning resources like RailsCasts, Destroy All Software, and the PICUS blog. It was just a good community to fall into.
When Rails isn't a good choice
Node.js make more sense for The Non-Web Internet: chat, email, SSH, Redis sockets, command-line API tools, custom network servers, anything synchronous. Anything that scales vertically, or has a significant amount of traffic (>10kRPM), should probably not be done in Rails.