It's for real-time music/audio apps, like virtual pianos, etc. These can be 100% local, and excessive latency is frustrating to the user.

It's not used for that. It's used for applications that need audio feedback after a trigger. In those cases 14ms+ is already way too much to the point of being unusable. For example: https://www.youtube.com/watch?v=_eE7NtK4jX8

It’s not for phone calls but real-time audio applications, e.g. music creation apps or games.

It will be useful for apps, esp. those targeting musicians. Iphone had sub-10ms latency for a long time.

Not only is 10ms roundtrip latency critical to the interactive audio type applications mentioned by others -- it is critical for VR too.

About 10 ms is the maximum latency that can be tolerated in music applications. Preferably it should be around 5 ms.

If you're a musician, you can easily notice when the sound doesn't come out when you press your finger on the keyboard or sing to a microphone. 5 ms is not noticeable at all, 10 ms feels a bit off but is tolerable, above 25 ms is clearly noticeable and very annoying (ie. it's no longer a musical instrument).

This latency mentioned is useful for music and VoIP apps.