PS4 games are heavily encrypted. Encrypted data looks like random noise. Compression algorithms work by finding patterns (e.g., "AAAAAA" = "6xA"). Random noise has zero patterns. Therefore, encrypting a file compression makes it small; trying to compress an already encrypted file does almost nothing.
A 20GB compressed file is much easier to manage than a 60GB raw ISO. ps4 iso games highly compressed
The world of compressed ISOs exists largely in a gray market. While developers use compression to fit games onto Blu-ray discs, third-party "high compression" is inextricably linked to the jailbreaking community. For a console like the PS4, these files only run on systems with modified firmware, creating a subculture that prioritizes "owning" the digital data over the convenience of official storefronts like the PlayStation Store. PS4 games are heavily encrypted