> already uncommon

It's definitely not uncommon though. Just to provide one example: how often do you use all the arguments to `.map` callback?

Usually you'd write something like `arr.map(x => x + 1)`.

However, to spell out all the arguments you'd have to write `arr.map((x, i, arr) => x + 1)`.

And there's tons of other functions like that in stdlib or 3rd-party libs that people use without passing or accepting all the args. That's why this optimisation is so useful.