The most common case I’ve seen is when you want to map using 'point free' style functions, i.e. “x.map(transformItem)”[1]. Another (more) common scenario—but not yet relevant in JavaScript—is piping/composing functions[2].

[1] https://en.wikipedia.org/wiki/Tacit_programming

[2] https://github.com/tc39/proposal-pipeline-operator/wiki