[pilif]

IPv6 NAT is generally discouraged and providers can gain huge benefits too from not doing NAT. NAT always implies state which needs to be stored somewhere. The moment you NAT, you very likely won't be able to do the routing in pure hardware any more, so throughput is an issue.

routing v6 directly is completely stateless. It can easily be done completely in hardware possibly not even requiring to store the packet anywhere, nor needing any knowledge of the protocols wrapped inside of the IP packet.

To do NAT, you need to know about TCP and UDP and about the various ports which means you need to look into the IP packet. To route v6, you just look at the IP packet.