There was a time when you had to haul around a vault of floppy disks whenever you go to work. You have to go through the trouble of labeling and arranging them properly if you do not want to lose anything. Despite that, digging through each floppy is still a tedious task, one that might require you to have someone else to do it for you.
Fast forward to the present: you can now have your internal hard disk in a case and bring it along wherever you fee like. More space for data storage, more data to store not just files you need in the office. You can bring along the music you work to at home, setting the good mood for a productive day. You can have your favorite video of your cat playing with tassels. No need for installations, just plug and play.