Of the 12 wireline ISPs here, 2 support IPv6. One of the two is available to 2% of the customers; the other costs 50% more than IPv4-only. For the extra money you get 5% of the upload + much higher latency. I'm looking into starting my own ASN just to get IPv6 here.
In the US there are millions of locations stuck with IPv4 only networks due to ISPs that are solidly committed to never supporting it.
IPv6 evangelists don't give a meaningful crap about those millions - and are happy to push IPv6 rosiness in a way that denies their existence.
Because of this, IPv6-only services can only ever get so far off the ground. An exciting service is less exciting when it's unreachable from point B.