For animations! But it's not the only case.
You can use it as a better replacement for frequent setInterval.
What if I told you that e.g. timeupdate of HTML5 video could be fired 4 times per second?
And you're building your own video editor and want to animate your custom timeline? Would you move the playhead or current time in your video editor 4 times per second? I believe you would want the smoothest transition you can do.
Then what about setInterval and check the video current time? That's possible, but how you would determine the frequency? 30Hz? 50Hz? 200Hz? That's a performance implication question already. Also if you would do any animations - high-frequency setInterval will flicker & shear your DOM.
Also setInterval is. known. for. it's. inconsistency.
Wouldn't it be better to rely on the browser repaint frequency? Especially handy when you want to do animations because it's invoked before the repaint!
If you need to invoke/listen to a function at extreme frequency mutating DOM, animating something, and you want to ensure the smoothness and consistency of what you do.
Or if you need a setInterval with less than 50ms and you want it to be somewhat consistent.
If you don't need to invoke/listen to a function very frequently and mutate your DOM.
Ask yourself, is there any other way?