EULA's are binding contacts. They are implied contracts, which are the weakest form of contract in the U.S. This makes them prime targets for litigation, but most EULAs are secured by legal precedants from other cases. ToS's are not contracts, but they are usually incorporated into EULAs making them, by proxy, a contractual agreement (different from an actual contract). Like any contract, its written up by a team of lawyers. By clicking "I agree" you effectively sign the contract as is. When "agreeing" to an EULA, you are not buying the software, rather you are buying a license to use the software...the disk, if any, are simply a physical means of you accessing the software's license. The disk, in and of itself, is not part of the software.
You know thats the thing that really makes me angry at these game makers because when i purchase something like a CD album of songs it belongs to me,when i go rental that belongs to the company i have rented from,so there are lots of technical issues out there for us gamers that we can never resolve because of company's like Steam/Blizzard.