The problem with the IPv6 migration isn't technical, but social. IPv4 was the version of the protocol that was active when the Internet "went pop", and as such

The problem with the IPv6 migration isn't technical, but social. IPv4 was the version of the protocol that was active when the Internet "went pop", and as such, many people (especially those who actually pay for the technology, rather than actually use it directly) think it is good enough. It doesn't help matters that workarounds and kludges like NAT are regarded nowadays as features instead of flaws.