Azure AD only got IPv6 support this year. Most corporate networks have not switched, whole most federal agencies have implemented IPv6(due to mandates), mobile carriers are heavily utilizing IPv6 and so are residential ISPs (Comcast and Time Warner have been deploying IPv6 since 2011)
Federal agencies turned on the Cloudflare flag that auto-translates incoming IPv6 packets to the IPv4 that they support for front facing websites. That checked the box and little progress has been made since then.
