Laptop as Desktop's external USB hard drive???

[IQLion]

Ok, so I don't understand why someone would want their laptop to be an external hard drive. You may save time uploading files to a flash drive or an external hard drive, but why would you want to carry your laptop with you instead of a flash drive(at least 20 times bigger) If you are too lazy to copy the files, get a dropbox, google drive, or get a huge flash drive(32GB should do), and a program that will monitor all your files and back them up to a flash drive everytime you save something. It might slow down your laptop a little, but you wouldn't have to worry about copying your files to a flash drive.