It's a chicken and egg problem - websites, etc don't want to enable IPv6 because clients have broken IPv6 implementations and that causes delays and issues, and clients have broken IPv6 implementations because the internet providers don't care to fix it because nobody uses it.

(Many computers THINK they have IPv6 connectivity when they do NOT and so if they see an AAAA record and try to connect to it, it can cause a delay while that fails. Most browsers are better at this now (they will try to connect to both and show whichever answers faster), but not all network things are browsers.)