Comment by mahboi

Yeah it's in the wild, but random crappy software isn't the reason all these big services are v4-only. Transitioning from v4 to v6 requires redoing your entire network, except you still have to maintain the v4 side until everyone else has done this. So it's not worthwhile unless you have an easy way to go v6-native and only use v4 at the ends, eg cellular networks.