'Not I' by Samuel Beckett

I've done a little research about the dramatic monologue 'Not I' by Samuel Beckett because the concept of the mouth is interesting.

Why cannot we see the whole actor playing why the background is totally black and only one part of the body we can see is the mouth? Beckett really wanted this piece to 'work on the nerves of the audience, not its intellect' (Beckett, 1974) and his idea was mouth 'an organ of emission, without intellect' (London: Vintage, 1990). It does sound very smart and my project is the little bit familiar as my video will be focused on my mouth, because I want the audience to focus on mouth movements and its position, encourage the audience to reflect and facilitate comparison, I don't want them to just watch the video of me singing.