A core problem of IPv6 adoption is the lack of user benefits
I've written before about some of the economic incentives involved with IPv6 adoption, focusing on who benefits from IPv6. Today I want to touch on this economic issue from another angle. Put simply, one of the big problems is this:
In many places, adding IPv6 to your network won't improve anything for your users.
Sure, from a geeky technical side it's nice to support IPv6 on your network and see ipv6.google.com and so on. Having your network and organization be IPv6 ready and enabled is clearly the right thing, a good thing for the future, and all that. But it's not essential. In fact it's usually not even beneficial, not even a little bit. If you add IPv6 to your network today, generally almost no one will notice anything different.
(Let's pretend that there are no bugs and systems that are unprepared to deal with IPv6 addresses and so on.)
At one level this is great; it's good that you can quietly drop in another network protocol and no one notices. At another level it's catastrophic to IPv6 adoption. IPv6 adoption is a lot of work in most networks; you've got a great deal to learn, a great deal to set up, a great deal to test, and so on. Unless you have a lot of free time it's hard to justify spending a lot of effort on something that doesn't actually deliver real improvements to your users, it's just the right thing to do.
(People like working on right things, but they inevitably get a low priority and thus not very much time. They're sleepy Friday and slack day and 20% time projects, not prime time work.)
Purely from a speed of adoption perspective, it would be much better if adding IPv6 was less transparent because it suddenly let people do things that they couldn't do before. Then you'd have a much easier time of building a case for spending significant effort on it.
(In fact it's my impression that many of the IPv6 adoption stories I've heard about are exactly from situations where adopting IPv6 did deliver real, tangible benefits to the organization involved. See eg Facebook's slides about their internal IPv6 usage, where IPv6 helped them deal with real issues and made their lives better.)