When you install Apache on the host then yes, you just need a rule to allow the port. But a container runs on a separate network interface, which means you also (1) need to know the name of the interfaces involved, which change for each container and their network mode and the host's network adapter and so on, and (2) set up rules to forward the port traffic between the container interface and the host interface.

I'm guessing you haven't checked to see what Docker is actually doing, or you've looked only at the OUTPUT and INPUT chains.

I'm also guessing that when you stop Apache you leave the ports open in the firewall. Which is bad practice. Docker takes down the rules when the container stops, which ends up as better security.

I sincerely hope you're not actually running a machine that's just a firewall away from the Internet, because blaming Docker for bad security in that case is very shortsighted. Docker is actually helping you by making correct and complete firewall rules.

podman, a drop in replacement for docker, does implement this in another way

Yeah? How does it do that?