ISPs don't want to implement it because their customers aren't pushing them to, because websites aren't typically IPv6-only, because that's a terrible business model.
So unless we force or incentivize ISPs to implement IPv6 access through law, it's going to be a long time before we hit the breaking point where something HAS to be done by ISPs
Here I'm assuming that infra teams already have a lot to do and would experience some harm having the government give them more user stories. Maybe not tons of harm, but what is the other side of the equation that justifies the harm?
It's a principal-agent problem. There are lots of people who want IPv6, but can't get it because their local ISP doesn't care.
Is it really such a great idea to force every single device on the internet to be globally uniquely identifiable?
We have run out of ipv4 addresses, CGNATs cause problems with self-hosting, ipv4 allocations are not fair and are driving up the cost of infrastructure/access. Particularly problematic in developing Countries.
Security is not an argument, ipv6 firewalls have existed for a long period now.
If we want to make the internet to scale then we need to encourage the use of ipv6.
From another angle, most people are walking around with a globally-unique identifier (IMEI) in their pocket with all kinds of sensors. Does using IPv6 materially change the situation for any attacker?