What is the sales pitch you would bring to the CEO of a Fortune 500?
When you buy or merge companies, and they both have RFC 1918 addresses, you'll probably have a conflict between the two entities. You'll probably have to implement NAT with-in your own network and hope the two sides don't have to talk to each other that much. (Or you completely re-IP the acquisition.)
With IPv6, either the companies will be using their own PI IPv6 space and/or they will be using unique ULA prefixes, so the chance of conflicts will be very small.
This at least was one of the business cases for Wells Fargo, "the fourth largest bank in the United States by total assets and is one of the largest as ranked by bank deposits and market capitalization":
If an internet service needs to distinguish users by IP address, say for spam fighting reasons, then IPv6 will provide finer granularity because the addresses are not shared by multiple users. Depending on how the ISP implements CGNAT, IPv6 may also improve performance and geolocation accuracy.
(They'd also be doing those ISPs a favor, because offloading traffic to IPv6 lowers the operating costs of CGNAT.)
I love IPv6 btw. I just don't think you'll see anything meaningful happen until FAANG drop IPv4 support. Imagine that. People would convert pretty quick if Google couldn't crawl your site or you couldn't buy an iPhone without IPv6...
IPv4 addresses are expensive right now. Registries run out of new allocations years ago, so if you ask them you'll be put in a waiting list[1] hoping one for a block to be recovered. To get one right know you have to go on the market and negotiate a transfer: blocks are selling at ~50$/address right now. The price more than doubled in the last year or so: people are even speculating on it [2].
[1]: https://www.ripe.net/manage-ips-and-asns/ipv4/ipv4-pool
[2]: https://teddit.net/r/investing/comments/qdple3/i_am_planning...
https://www.internetgovernance.org/2021/08/19/a-fight-over-c...
(Although, people rent apartments with break-even periods well beyond 10 years, so maybe 2-3 is still fine.)
This has been happening for years with VPSes.