Will you repeat the whole dance when you need a second extra octet? There are good reasons IPv6 is designed the way it is.

They considered 64 bit addresses at first but they didn't want to ever risk running out again so they doubled it again.

Try to remember it's not just about the sheer number of addresses - you also want to allocate them in big blocks so that few people ever need to expand their blocks, and they can split their big block into more blocks that are still big.