Ruby is used in a lot of places where Rails isn't, by a few large companies. The one that comes to mind is Stripe, which has at least a couple hundred engineers writing Ruby code that has nothing to do with web development (much less Rails).
While Rails certainly did a huge amount to make the language popular, there's lots of things Ruby is good at aside from concatenating snippets of HTML.
Actually, that being said, while maybe 90% of personal Ruby projects don't use Rails, a good half use ActiveRecord in some capacity. I wonder how much that makes it a Rails project, by some reasonable definition.
And many people use Homebrew on OSX, or Linuxbrew (homebrew for Linux -- useful especially for users of beowulf clusters who often don't have rights to install anything except in their home directories), and brew and its formulas are written in Ruby.
While Rails certainly did a huge amount to make the language popular, there's lots of things Ruby is good at aside from concatenating snippets of HTML.
Actually, that being said, while maybe 90% of personal Ruby projects don't use Rails, a good half use ActiveRecord in some capacity. I wonder how much that makes it a Rails project, by some reasonable definition.