In theory yes. But what about users that are mobile on a call and even when they "push" to talk, ambient noise from the metro, crowd, or traffic is present enou

In theory yes. But what about users that are mobile on a call and even when they "push" to talk, ambient noise from the metro, crowd, or traffic is present enough to be troubling? You don't always get to choose if background noise is present. Also, you just asked that people push a button, and wear a headset. That is a lot, and this is about lowering the bar needed to get a good experience.