Biggest "excuse" is usability: IPv6->IPv4 failover where the IPv6 DNS records are busted make a whole lot of sites unusable. Basically, the AAAA record provid

Biggest "excuse" is usability: IPv6->IPv4 failover where the IPv6 DNS records are busted make a whole lot of sites unusable. Basically, the AAAA record provides some broken IP6 address, and the browser then just "site not found, NXRECORD", even if there's a perfectly valid A record for the same. If a company doesnt have an AAAA record, it works fine. Its when the AAAA record is busted (but present) is where you will see loads of weird and bad stuff.