Is it that difficult to setup, or are people biased against it when something they've got works, and something new doesn't?
When IPv6 doesn't work, it's easy to blame it, turn it off and stick with IPv4 because it works. When IPv4 doesn't work it's a problem that has to be fixed to access the vast majority of services online.
If your DNS can't resolve A records, you'd immediately complain and get it fixed.
When was this? For a long time IPv6 suffered from people running services over tunnels via tunnel brokers, which resulted in horrible performance, MTU issues, timeouts and so on.
I have noticed recently that the situation has improved a lot, with more and more "real", native deployments coming online.
Which researching before posting this answer, I just noticed that it is due to DNS timing out for IPv6 requests [1]. IPv6 is hard to set up.
[1] https://www.sixxs.net/faq/dns/?faq=ipv6slowconnect