There are many reasons a person can't simply "copy" a console game onto a fresh dvd-r and use it.
First, Console games (and any others usually) have special copy protections, usually in the form of embedded codes, that prevent proper copying. They can also include encryption, which means if the disc is copied, the encryption will read the data differently, and let the hardware know the disc is copied. These encryptions and copy protections are to prevent piracy, that is, the copying of the game. According to the license agreement... you can't at all for any reason.
Second, just because the MEDIA is DVD, it doesn't mean the DATA it contains is written in a language your PC will understand. It might still be "ones and zeros" but the disc content, order, placement, etc, can all be different. For example, a game disc could require a dvd to have a blank space in the middle, which burning software wouldn't "copy." Then the game loads, and looks to see if the expected "blank space" is there, and if not, the software also knows its been copied. There are 10,000 of tricks like this to prevent piracy.
So the mods to hardware and software are made to circumvent anti-piracy restrictions. In fact, "chipping" your Playstation is illegal, not because doing so is intrinsically bad/dangerous/whatever, but because TRADE agreements made it illegal for you to do so, which made it safe for importers to import.
And why the anti-piracy stuff? To protect the rights and money of the people who made the game.
Any other questions?