This is the strongest selling point. The PS3 has a massive library, but many digital-only games have been delisted from the PlayStation Store due to licensing expirations (e.g., DuckTales Remastered , various Transformers games). PKG lists allow you to access this "lost" library.
Using PKG files on a PS3 connected to PSN can result in a console ID ban (permanent online ban). Always disable syscalls or use PSNPatch before going online. Ps3 Pkg Games List
Essential packages that fixed bugs or added new chapters to stories like Assassin's Creed [2]. This is the strongest selling point