&gt; Sounds like Stockholm syndrome. Are there any desirable properties of NAT that can&#x27;t be duplicated with a firewall?<p>That they are widely deployed, reasonably predictable and quite transparent to the user.  Which means that in the default configuration a user has a secure setup that apps however can partially circumvent to enable incoming traffic on UDP ports.  Many computer games or P2P systems exploit this setup quite successfully to set up P2P networks without any user interaction.