Curious why the rfc didn't choose base64 as the representation format. It won't change what it looks like on the wire but will result in shorter addresses that

Curious why the rfc didn't choose base64 as the representation format. It won't change what it looks like on the wire but will result in shorter addresses that can in part have some meaning. Matter of fact has there even been such a proposal. I naively think '2001:ALN:LabNet01::' or somethig of the like is not only better but displaces some of the need to use dns (at least in a lan). I am so curious about this, I hope someone more knowledgeable can explain.