Comment by teraflop

The thing is that the abundance of IPv6 addresses enables fewer prefixes to be used, by allowing addresses to be allocated in much larger chunks.

For instance, Comcast (AS 7922) owns about 2^26 IPv4 addresses, distributed across 149 different prefixes. Almost all of these prefixes are non-contiguous with each other, so they each require separate routing table entries. Comcast can't consolidate those routes without swapping IP address blocks with other networks, and it can't grow its address space without acquiring new small blocks. (Since no more large blocks are available, as this article discusses.)

In contrast, Comcast owns about 2^109 IPv6 addresses, which are covered by just 5 prefixes (two big ones of 2^108 each, and three smaller ones). It can freely subdivide its own networks within those prefixes, without ever running out of addresses, and without having to announce new routes.