It's not about being perfect, but learning the proper way to do things because 1) they learn more 2) it's applicable to things outside of Minecraft 3) Hamachi is Satan in binary form.

Port forwarding is a process that benefits anyone in many ways. It'll make your network more flexible and allow you to create a better connection to many other things, such as Xbox Live, PSN, and virtually any online game. If people want to run servers this is something they should attempt first and use Hamachi as a very last resort. It shouldn't be a step skipped because hosting a server means you should understand at least some fundamental networking if you want things to run smoothly. Did I mention Hamachi is evil?

No this doesn't work depending on the network setup. External connections(other players) will need to connect via specific ports, but routers often close these off. If you have a router you will need to forward ports in order for others to connect. It's a fairly simple process.