first of all i must say that i don't know anything about coding and those things,the only think i know is press the run cdvd button to play .

and the question is....

why don't you make a program to read the ps2 code instead of emulating the hardware?

If you don't know anything about coding, how do you supposed to understand the answer? Well, just imagine that program would recite this "code" loud to speakers. And? Such "code" would not be executed. So you want to know why developers emulate the whole system, that allow this code to be executed instead of silly reading?

To put another way: An emulator must do both emulation of machine code and emulation of PS2 hardware. You cannot have an emulator without emulating both things.

Technically though it's all hardware. The "code" is run through a combination of CPU emulators (MIPS R5900, MIPS R3000A, and other sub-processors). These are hardware devices, much like the Intel or AMD CPU in your desktop machine.

So yes we "read" the ps2 code already.