Even among the top websites, there are a lot of them that don't even do dual stack. Let alone IPv6 only. (e.g. Twitter) Also, only using IPv6 is cutting out 75

Even among the top websites, there are a lot of them that don't even do dual stack. Let alone IPv6 only. (e.g. Twitter) Also, only using IPv6 is cutting out 75% of the world population, according to Google. https://www.google.com/intl/en/ipv6/statistics.html https://www.google.com/intl/en/ipv6/statistics.html However, public-facing dual stack but internal IPv6 only is done at e.g. Facebook IIRC (see https://code.fb.com/?s=ipv6 https://code.fb.com/?s=ipv6)