In tools like Node-Red (https://nodered.org/), although they have their own implementation.

Any visual coding scenario really.

I made a similar (though less complex version) of this for tech trees.

https://ldd.github.io/react-tech-tree/#examples

So the answer is, to make games!

I used it my library for my own game here:

https://ldd.itch.io/nu

You could build a WebAudio synth / node chain with this, it's much better than looking at code.

Or set up CI pipeline with this.

Or in cases when you want end users to set up flows, but they can't code.

It's a library that could help you to build an UML editor or a node-based compositor for example.