easier to play games without disk?

with the release of the new dashboard, xbox experience, come the ability to store or rip or backup (i dont know what exactly id going on) your disc's on the xbox hard drive. now it may sound sweet i just thought it would make it easier to move my xbox and not have to worry about a cd case for games. but when i completed the backup, i still needed the game disc. my question is, what part of th game was copied? why does it still need a disc? and what part does it look for of the original disc before the xbox allows you to play. couldnt i just make a program that says "yes the game disc is in the drive" for any game and play it off the hard drive? or is that too complicated?