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.