I can see multi-channel audio as a feature request if After Effects was good at editing videos, but if you are only creating shots that are going to be edited into sequences to make scenes and the scenes are going to be edited into movies, I don't think the feature would be of much use to most users. 

How long are the videos you are rendering in After Effects that require multi-channel audio? Almost everyone that I know in the visual effects, motion graphics, and animation industry, uses AE to create shots and edit the final movie in an NLE. I don't know anybody that usually creates a whole movie in a single AE comp or in a single 3D project. Polishing outside an NLE is just too tedious.