because it was never released for the PlayStation Portable (PSP). It was a PlayStation 3 exclusive RPCS3 Wiki

If you own original PSP UMD discs:

Both titles deliver console-quality experiences, complete with brutal combat, epic boss fights, and the signature quick-time events.

: Some sites offer "Highly Compressed" 200MB to 1GB files. These are usually the original PSP God of War games renamed to attract downloads.