Or...
Emulator's developer are abusing questionable little loopholes to spread piracy and rom dump in their sites.
Why emulator's developer never create emulators that only play official media?
No, the courts have been pretty explicitly clear on this before. No loopholes or legal games. This here with the OP is all just the result of abuse of CR laws. They lay claim on things like firmware, DRM, hardware keys and other such things on YOUR hardware, to threaten CR lawfare. It's not even clear if such tactics would work.. But nobody dares be the person to test it out.
It's the same with copying media you own. So many people are completely unaware of their rights and where the law stands on these types of things. Did you know that it is not just perfectly legal to make as many copies of media as you want for personal use or backup, it's arguably a protected right? As long as you aren't selling them or abusing it.
In both cases they also use questionable criminal laws protecting DRM to de facto circumvent your rights. It's one of the (many) reasons the DMCA needs axed ASAP. As a first step in much needed CR reform.
Big media has gotten smarter and pushed everyone away from physical media and into gated media viewing environments. Environments with tech and legally questionable ToS's that can ban you for trying to take control of your copies of media. We seriously need some major legal pushback.
Some have. But in a lot of cases it's hard because the protections are built into the disk drive etc. (i.e. no way to validate that a media is 'legitimate') You can't recreate that kind of hardware protection. This also ignores the reason why a lot of people want to do so anyway. Exercising their right to backup their media. Disks get scratched and carts get old and broken etc.
Hell, most of the old (MY old) games i replay are on emulators. Hardware too gets old and breaks down. There are mods, performance and other reasons why someone would want to too.