It is important to understand the legalities surrounding BIOS files:
Core hardware initialization for emulation software Why Is This BIOS File Necessary?
Manage internal clock data, memory card formatting, and initial hardware pathways.
The SCPH39001BIN file serves several purposes:
Without a valid BIOS file like SCPH39001.bin , an emulator cannot interpret game instructions, handle save data formatting, or boot into the main gameplay screen. The Legalities Around PS2 BIOS Files