If you are looking at this from a PC emulator perspective using ShadPS4 :

One of the strongest arguments for the superiority of PKG files is access to content that cannot be bought on a disc.

For a "better" workflow, these tools are highly recommended by the community: PS4-PKG-Tool

In the ecosystem of video game preservation, language matters. While the internet is flooded with search terms like "PS4 PKG ROMs," the terminology is a bit of a misnomer—a collision of old-school nostalgia and modern technical reality.

Furthermore, tools like pkg2zip or Fake PKG Generator allow users to repack games with zStandard (zstd) compression—yielding 20-30% smaller file sizes than the original Sony format. Smaller PKGs mean you can fit 20 high-end AAA games on a 2TB drive instead of 14.