You have to change the file-system ON the USB drive, which is why they say it ruins the drive. Normally, the file-system on the drive is meant to be accessible by the current OS, and perform operations such as storing, reading, and writing. This is no where near boot-able. To make it boot-able, you have to throw up some fancy shit that I feel you don't need to know, and then put the OS on it. Just putting the OS on a flash drive and expecting it to run is like putting wheels on a refrigerator and expecting it to drive.
Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning. -Rick Cook