alt Hacker NewsAnd because it's a layer 7 thing, so it only required updating the server and client software, not the OS... and only the client and server endpoints and not the routers in between... and because we only have two browser vendors who between them can push the ecosystem around, and maybe half a dozen relevant web server daemons.
Layer 3 of the Internet is the one that requires support in all software and on all routers in the network path, and those are run by millions of people in hundreds of countries with no central entity that can force them to do anything.
HTTP->HTTPS is only similar in terms of number of users, not in terms of the deployment itself. The network effects for IP are much stronger than for HTTP.
They don't "sorta" use v6, they're properly using it, and you can certainly go v6-only. I'm posting from a machine with no v4. Also, if you want to go there: HTTPS was released before IPv6, and yet still no browser is HTTPS only, despite how much easier it is to deploy it.
I know they aren't very comparable in a technical way, but look at the mindset. IPv6 included decisions that knowingly made it more different from v4 than strictly needed, cause they wanted it to be perfect day 1. If they did HTTPS like this, it'd be tied to HTTP/2.
Most browsers now discourage plain HTTP with a warning. Any customer-facing server basically needs to use HTTPS now. And you're rare if you actually have no ipv4, not even via a tunnel.