Comment by Aurornis

I often put AirPods in and turn the noise cancellation on, but don't play any audio. Many other commenters mention the same thing.

Different people have different levels of ability to filter out background noise. Some people can focus and ignore the outside world so much that you have to wave a hand in front of their face if you need their attention. Other people can't help but parse background conversations and noises all around them.

Noise cancelling headphones level the playing field for people in the second category: It allows them to dial down the distractions and focus like the first group when their environment is fighting hard against it.

Even listening to background music has the same effect for many people. Music, especially familiar music, is not necessarily engaging enough to pull people out of their relaxed states and focus on the music.