Q: A purist network engineer argues that with the adoption of IPv6, NAT (Network Address Translation) is dead and should never be used. Why does IPv6 eliminate the need for NAT?

NAT was heavily popularized primarily as a hack to solve IPv4 Address Exhaustion. Because there are only ~4 billion IPv4 addresses, we hide thousands of private corporate devices (RFC 1918 space like 10.x.x.x) behind a single public router IP via NAT. IPv6 provides 340 undecillion addresses. Every grain of sand on Earth could have a unique public IPv6 address. Because there is virtually infinite supply, every server and device can have a globally unique, publicly routable IP address natively. NAT is fundamentally no longer required for address conservation. (Security is handled by strict stateful firewalls dropping inbound traffic, not NAT).