The cell phone carrier market is the classic example of a "confusopoly" where the dominant market players make it as hard as possible for consumers to make fully informed decisions. None of the carriers actually has a monopoly outside of a few isolated areas.
https://en.wikipedia.org/wiki/Confusopoly
Acoustics make it impossible to do good noise cancellation using just an app. You really need a specialized microphone mounted directly on the headphones.
Sure you need a high quality microphone on the earphone - but that's men's , could be very cheap in volume. And the rest is something interface chip on the phone, and than some digital logic which is cheap.
It stops working, because the latency is too high for the inverse-phase signal to match up with the unwanted incident signal it's intended to cancel.
You could have a low latency digital processor in the phone/soc. At that level, digital is cheap.
Of course the other part is that high-frequnecy noise is hard to cancel. But still Bose does a great job.
You can't have a wireless round trip with latency low enough to work.
Another place where the smartphone could help with costs: currently great noise cancelling earphones are very expensive($300) .And in general are well loved by those who can afford them.
but what happens if we remove most of the hardware(cheap) and compute($0 on phone) to the phone ? And create place in the app store for noise-cancelling apps ?
[1]http://5gwnews.com/index.php/90-r/670-wireless-abundance-is-...