Rails was the first non-enterprise, opinionated, and complete Web framework. It had built-in pluralization of nouns! There are database migrations, distinct runtime environments and many more fascinating tools! A huge bag of helpful methods, which abstract common tasks and help code to read beautifully. It takes mere minutes to spin up a server and deploy to Heroku, for free!
We use Rails because it solves its specific problem more efficiently, 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 and 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.
When Rails isn't a good choice
Go or Elixir/Phoenix 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.