Initially mobile network bandwidth was very limited and so CSR + single-page web apps was a way to cut down on full page loads. Lean RESTful endpoints could be

Initially mobile network bandwidth was very limited and so CSR + single-page web apps was a way to cut down on full page loads. Lean RESTful endpoints could be optimized to only return what the client actually needed in a given context in order to update runtime state without having to fetch and re-render anything superfluous.