Its incompatible with IP v4, has a stupid addressing scheme, it requires new router hardware and software for isps to buy and nobody is using it because of all the aforementioned issues.
What could an increase in the IP address space do to be compatible? I can think of a couple things to be partially compatible but IPv6 already does those.
And by "stupid addressing scheme" do you mean it's too big, or what? You can ignore all that stuff with mac addresses and make all your addresses go like prefix:subnet::1 prefix:subnet::2 prefix:subnet::3 if you want to.
You forgot, they're nowhere as easy to remember as v4. If you're used to remembering phone numbers; important v4 IP's aren't that hard to mentally internalize.
Screw DNS. Screw the recommendation to stay away from IP's. If it's important enough to be on the network, it's important enough to have a static IP.
You're being downvoted, but, last 3 ISP's I used didn't support ipv6. First one didn't support ipv6 at all, second supported it, but was incompatible with my router. And I didn't care about it after that. Hardware incompatibility is a huge roadblock for ipv6.
IPv6 is well over 20 years old. In fact, IPv6 is now older than the IPv4 Internet was when it went mainstream back in the mid 90's. There is really no excuse not to support it...
And by "stupid addressing scheme" do you mean it's too big, or what? You can ignore all that stuff with mac addresses and make all your addresses go like prefix:subnet::1 prefix:subnet::2 prefix:subnet::3 if you want to.