Responsive is the developers' framework.
Accessibility is a first class concern in Responsive and as such each component and plugin within the framework has been carefully crafted to be fully accessible to keyboard and screenreaders.
Responsive has built-in right-to-left language support for all its components, even touch events have been altered to provide the best possible experience for right-to-left users.
Other frameworks are too design opinionated and style heavy. They're great for prototyping but every time you start a real, front-facing, project with them you have to overwrite lots of designer styles that do nothing to add to the functionality of the website. That costs developers time and money.
Responsive has been built with that in mind. It is the result of thousands of hours of real, client driven web development and testing; specifically developed to be as lightweight as possible to prevent the need to undo styles set by the framework itself and allow developers to write efficient code and lower costs.