The big issue is that the router vendors hated it, the OS vendors hated it, the programming language people hated it, and the software writers hated it. How do I know? NOBODY WANTS TO ADOPT IT except by force, even now.
Worryingly, pro-IPV6 people are consistently arrogant and dismissive. Essentially their argument always boiled down to "ha, you'll be forced to use it eventually and then I'll be RIGHT!!!" which is why IPV6 people hate NATs with a vehement irrational passion, because it floated IPV4 for, what, two decades at least?
I'm guessing it is because IPV6 was a tossed-over-the-wall protocol that didn't get reference implementations from the biggest router vendors first. Here's a very very very very very very troubling link:
https://www.cisco.com/c/dam/en_us/about/ciscoitatwork/networ...
That is Cisco bragging about it's IPV6 website on a pdf from 2011! 2011! Fifteen years after the birth of the protocol. If Cisco did not have an IPv6 site up until FIFTEEN YEARS after protocol definition ... oh god.
Comcast routers weren't IPV6 functional back in 2015, at least they weren't on my cable modem. If an ISP that makes bank on renting and turning over its consumer routing hardware can't roadmap ipv6 adoption within 22 years... ugh.
And my biggest complaint about ipv6 is that they didn't increase the number of ports. Really. We have to keep shoehorning apps into 64k ports rather than a sensible 4 billion, but maybe there's some OS mapping concern with that, doesn't matter, the ship sailed.
https://en.wikipedia.org/wiki/Internet_Protocol_version_4
Somewhere in IPV4 is an options header (up to 40 bytes). Why that didn't provide the necessary space for some degree of backwards compatibility somehow is beyond me.
What should have happened is that the big router vendors got together and agreed on a standard protocol. Then the major OS vendors and language standards bodies got together and made reference implementations for basic networking.
Once that was working / adopted by next gen hardware and software releases, then things might have gotten rolling.
I mean, how much work was that relative to the mind boggling amount of work done to implement NAT and firewall traversal/busting code in, say, Skype? Ever seen those whitepapers? Wow are they doozies. Holy crap are people willing to write code.
This is all screaming at the darkness.
