In need of some cedar for a coolidor

[DeeDubya]

I've wondered the same thing. But then I think for the RH, cedar acts like a buffer that helps maintain a constant humidity by containing the moisture when a humidor is opened. I'm sure there is a substantial amount of moisture in the cedar. Hence the reason to properly wipe down a new humi because the cedar soaks up so much moisture.
For the aging, this is pretty informative: http://cigars.optempo.com/tag/cedar/

Also, some cigar companies choose to wrap certain ones in a cedar sleeve. Surely there's a better reason than appearance alone.