Why Would You Use the Non PAT Version of NAT?

This is a good Question and the Book Side Steps the Question

NAT

NAT (Network Address Translation) is a 1 for 1 translation of Private Addresses for Public Addresses

It Does Not Save you any IP Addresses

Inside

Outside

10.1.1.10

10.1.1.11

10.1.1.12

11.1.1.10

11.1.1.11

11.1.1.12

Aside from some debatable and somewhat superficial security enhancements, NAT is used to explain how the wider Technology for PAT works, for example:

DNAT – Dynamic Nat

NAT with Dynamically assigned addresses from a pool of addresses

SNAT – Static Nat

NAT with Statically assigned addresses from a person

So Let's Focus on PAT