Practical example where micro task queue is useful in Event Loop

I learn that there are three queue in Event Loop.

1. macrotaskqueue

• related with setTimeout, setInterval, event(user gesture) task, event handler, network response etc..

2. microtaskqueue

• related with MutationObserver, Object.observe, Promise
• have higher priority than mactotask queue
• main thread work on this queue until it is empty
• rendering will be delayed until this queue is empty
• a task inserted into microtaskqueue in processing microtask will be executed at that iteration ( = microtaskqueue should be empty before going next iteration or rendering)

3. animationframequeue

• callback function of requestAnimationFrame() is inserted in this queue
• a task inserted into animationframequeue will be executed at next iteraction(unlike microtaskqueue)
• tasks in this queue will be processed right before rendering

Yes,, But What I want to know is that

• Is microtaskqueue really needed?
• What is practical(useful) example of using microtaskqueue?
• Why the computer guys made this queue? what’s the motivation?

Check please, I need your helps