Re: "We have now run out of IPv4 addresses"
Even if they had added only one byte to the IPv4 address it would still have required a complete redesign of every network stack in the world, an upgrade or replacement of every hardware network device in the world and a complete reconfiguration of allocations.
Which of course wasn't necessary for IPv6 given it's backward compatibility.. No, wait..
One reason was fending off the ITU, because an ability to just slap on a country code prefix would have been too easy, and too beneficial for national/international routing. Basically the IETF mostly ignored a problem the voice world had solved a century ago*
National networks would have resulted in some reconfiguration of allocations, or it'd just be left as a larger version of the old v4 'swamp' space. Changing hardware/software stacks isn't really a good reason given that had to be done anyway to support v6.
(*OK, there are some fun examples, ie Dublin's choice of numbering)