@paulehoffman @b0rk @spamvictim @andy
There are many angles here, so I'll provide one or two.
1) Having a large amount of IPv4 space made address planning and structured addresses easy. For example, MIT used to split up 18.0.0.0/8 in a structured manner -- for example buildings often got a /16. My undergrad dorm didn't *need* 64k IPv4 addresses, but being able to look at the second octet to know where it was turned out to be super convenient.
This is actually one of the huge benefits of IPv6, especially when people treat it as its own things rather than just as "bigger IPv4". If you get you address plan right then you can have structured addresses. As a large scale operator this turns out to be super convenient.
For example, if an organization has a /32 then they can slice this up in various ways. For example:
* Have a /48 per site, and then have common structure within each site.
* Have a /36 per function (prod servers, lab/QA, clients, etc) then have a /48 per site within that.
That sort of structure makes IPv6 addresses actually easier to work with than IPv4 -- it's not like anyone managing a network with hundreds of thousands of nodes is typing IP addresses by hand or memorizing them.
While structured addressing sometimes happens in RFC1918 space (eg, for K8s clusters in net-10), it is much easier to run out of space in IPv4 this way in ways that get you stuck, especially if you ever need to connect multiple environments together. While 24M addresses in 10.0.0.0/8 sounds like a lot, it turns out to be not big enough for structured addressing in large compute environments, or even for unstructured addressing for large ISPs with many tens of millions of subscribers.
