The only time I've ever really needed recursion is when I'm doing something that needs to map out some sort of tree or heavily nested object.

One example that comes to mind is when I needed a function that acts like querySelector, but also searches through shadowroots. Since querySelector does not natively search within shadowroots, I had to write a recursive function that basically starts at the root and recursively searches each node for a shadowdom, goes inside, and runs itself again.

It's definitely not the most performant solution, but it is sometimes necessary.