The point of Close ups in stop motion films

Close ups have several functions in film. 

A one minute video tutorial:

close-ups blog post
Obviously they convey detail but more importantly they can show a character's emotions more effectively than a long shot which relies on gesture. A close up can imply an unseen observer. A close up may feel intimate or scary depending on how it is used
camera angles 
Extreme close ups and unusal angles can create surprise.
reasons for extreme close ups
A close up may help in continuity by coming between long shots that would otherwise seem jerky due to a change in perspective or angle.

For these reasons, I think it's important to duplicate a character's face on a large scale in a stop/start animation. In this video, I demonstrate how you can do this to simulate the use of close ups in cinema films. 
My characters are made from foam cut to shape and sewn together. The shapes are derived from photographs using a light box, as you can see in this one minute tutorial: