I Think they use it more inside your own private network.

You can make use of proxy arp and destination and 1to1 NAT to expose internal services to the Internet. You could also route the additional addresses internally and assign public ips directly to other devices.

If you compare Dynamic NAT and PAT side-by-side for performance, you'll find that both are about the same. The most performance-intensive part of both technologies is the rewriting of the packet, and since both technologies need to do that, CPU load should be about the same.

The largest benefit of having more public addresses is that you can expose internal services to the public internet. For example, let's say I'm the network administrator of a small shipping company. At our headquarters, I need to provide internet access for 200 hosts, as well as host a web server that allows our customers to order online. The easiest way to do that is order two public IP addresses from my ISP, use one of them to provide access for all of my hosts via PAT, and translate the private IP address of the web server to the second public IP address via Dynamic NAT.

Could I do that with a single public IP address with PAT? Sure! I can port-forward ports 80 and 443 to the web server, and have my hosts use the rest of the ports available. However, that doesn't scale very well - what if I have two web servers that I need to expose to the internet, both of which are listening on port 80? I would need to set up a reverse proxy server, then forward traffic on port 80 from my WAN router to the reverse proxy server, then configure the reverse proxy server to forward and receive requests on behalf of the web servers depending on which website the user is accessing. Purchasing public IP addresses for each of my internal services that need to be exposed to the internet is much easier in the long run, albeit arguably more expensive.

I remember the days when that was the ISPs only answer to "I want to use more than one computer". They didn't officially support (nor lease) routers. And public IPv4 addresses could be had for like $5-10/mo (at least for residential). Ahhhh, back before the internet was so toxic. You got me reminiscing.