OTOH I'd be amazed if no-one's built an SPA in production with React and nothing else from the React ecosystem. What would be so hard about that? You can totally use it as just a view layer, if that's what you want to do. Granted, you probably use other non-React libraries, but that's not what we're talking about.
You can also have a "view layer", some control flow behavior in simple higher-order components, and then stores and actions that are simple plain-ol'-Javascript without needing a framework dep. The idea that a React app without Redux and react-router must simply be a brainless view layer is reductive and misleading.
Right, I'm sure there's some Rails and Django folks out there just using React as the view layer. Plus as someone mentioned above, Next.js is one of the simplest ways to do full stack React.