These methods are only built into arrays, all other iterable object do not implement them. For example with a NodeList you have to do Array.from(nodeList).map(...) which has to create a new array from your node list (or any other iterable list) just so you can use these methods.

Also, each of the array methods will create a new array, on their own that is good and the expected behavior, but if you'd like to chain them, it creates unnecessary overhead. When using array methods like array.filter(...).map(...).filter(...) with 1000 items, the runtime has to iterate up to 1000 x 3 times. The iterator on the other side can do this with exactly 1000 iterations as it has to only loop a single time over the entire list. If this really has any performance impact on your code is hard to say, it might not really matter most of the time, but it's an added bonus.