why do we never see the face of the cheerful soldier in the red badge of courage?

We never see the cheery soldiers face because Henry never sees his face. The cheery soldier stands over him, bolsters him, and carries him, but Jim is taken be the man's voice..... he never looks at him.

The youth did not look up, but he assented with thick tongue. “Uh!”

The youth, with his chin still on his breast, stood woodenly by while his companion beat ways and means out of sullen things.

A warm and strong hand clasped the youth’s languid fingers for an instant, and then he heard a cheerful and audacious whistling as the man strode away. As he who had so befriended him was thus passing out of his life, it suddenly occurred to the youth that he had not once seen his face.