Well the data shows they are in fact using it. Most people use their ISP router which in these carriers would be setup by default to use v6, plus any router bought in the last 10 years would support v6 and probably use it by default.

I'm on a large ISP provider and they do not have IPv6 in my area, a new build with fiber to a access point that turns it to cable on the house. So there's that.