Why shouldn't someone assign a public IPv4 address to a server? The whole NAT game is just that, a game.

Also, NAT gateways cost money in AWS, so much that it is a running joke:

https://twitter.com/QuinnyPig/status/1294047698560012289

https://twitter.com/QuinnyPig/status/1293366642567651330

NAT doesn't add any additional security, Security Groups are fantastic at allowing you define your ingress/egress between instances and protecting them from harm.

All my instances get an IPv4 address an an IPv6 address by default so that there is parity. The fact that the IPv4 address still goes through some sort of NAT on AWS's side (1:1 but still NAT) kind of bothers me.