IPV4 is in my opinion fundamentally broken for the use it has been given.
So no wonder they wanted to do something different, and prevent NAT. NAT lovers keep calling for NAT66, but that is unneded.
Just go here please:
No need for NAT in ipv6.. and this is not a mistake, it is on purpose.
Look at the ridiculous bottlenecks some mobile phone companies have in their CPDs.. that would not happen with a properly deployed IPv6 network!