It's not that I can't, it's just it's a pain in the ass.
You need a special tool to read the drive's code manually off of the drive, you can't it obtain via hookup. An Xbox's drive contain an individual code, which is why you can't just swap your drive for a new one, unless you get the drive keys. Then once you have it you need to completely erase the firmwire on the drive, only then can you connect.
Until someone finds an easier way, many people prefer just to either buy another drive and "spoof" it (marry it to the xbox) or just not flash them at all.