AFAIK anyway, Webpack isn't automatically installed with every Rails app but is easily available via https://github.com/rails/webpacker https://github.com/rails

AFAIK anyway, Webpack isn't automatically installed with every Rails app but is easily available via https://github.com/rails/webpacker https://github.com/rails/webpacker. So it's not "bundled" necessarily all the time, but is quite trivially added to a Rails project. If your question is more like "why the hell would you ever want to run Webpack and Rails simultaneously together": You will increasingly find tools you want to use that more-or-less require Webpack (or a similar JS build tool). Because of things like e.g. the asset pipeline, it's extremely frustrating trying to get those tools to work in concert with each other as micro-services that know nothing about each other. It's much easier to use something like Webpacker so they can play nicely with each other.