Features

[LunaMoo]

There's two kind of emulation, low level which emulates hardware and high level emulators which translate whatever games needs to run on a modern operating system.

Most of the time the reason to emulate hardware is an attempt of a more accurate emulation as such ends up much heavier, but as a side effect both can and requires official software.

Things like BIOS or firmware are often required due to encryption, other security reasons or some overlay features that can be accessible from the game and as such required by some high level emulators as well, but that does not mean they actually can run operating system of the console and give you full native experience, they don't, outside of few bad cases from the distant past where it improved compatibility there's no advantage to that either, quite the opposite it brings legal issues and reduces user experience.