It's not just "the ROM in it", it's "the ROMs in it". Single-rom games don't benefit from containers. The whole point of treating all games as containers is to

It's not just "the ROM in it", it's "the ROMs in it". Single-rom games don't benefit from containers. The whole point of treating all games as containers is to allow multi-rom games to be free of metadata. 30% of NES games, 1% of SNES games, and most arcade games are multi-rom. In order for the emulator to tell contents apart without metadata, you have to have a naming scheme. So, for example, Galaxian.fc.zip would contain "program.rom" and "character.rom". Currently, those pieces are blobbed together with a header in front. Thus you can't open a .NES file in your file browser and see if it has a character rom, what size it is, what sha256 it has. This causes massive tedium with NES dump verification since you can't assume anything at face value. All parts and values are obscured and need extracted. The other reason metadata is evil is that it's a royal PITA to maintain. It's far easier to update your emulator than thousands of individual files. Do not listen to anyone who tells you that we need to drag licensed games into the metadata mud for the sake of unlicensed games. They are pulling your chain, an unlicensed db for nes is entirely feasible, or even the mapper number applied to the extension ala "Cheetahmen II.224.fc.zip". MAME did this right with a database and NEVER writing inside the container, but only because their hand was forced into it. So many arcade games have 3 or more roms, so they were never tempted to take shortcuts and blob shit together to avoid zip containers. Then they screwed up their own good fortune with some truly bizarre stuff. Google non-merged vs merged and behold threads and threads of confusion. Now weigh that confusion against the supposed benefit.