Traditionally, when a home user sets up a home network, a lot of manual configuration is needed. While the IPv6 configuration can be done in an automated way by using Prefix Delegation, the IPv4 setup requires manual configuration of subnets and routes within the network. The mechanism of Link-ID describes a way to derive IPv4 subnets from the IPv6 subnet, so manual configuration of the first is no longer needed.
The internet is still expanding. Even more, we're facing a major explosion of the number of devices connected to the internet. The rise of smartphones, wearables and the Internet of Things are evolutions that will expand the number of connected devices to numbers unseen so far. The transition to IPv6 is inevitable, but why does it seem to take so much time?