Do you dual-boot Windows and Linux? If you do, then you’re probably familiar with the different file systems that the two operating systems use and the difficulty in transferring files between the two. While most modern Linux operating systems can read and write to Windows file systems (NTFS and FAT/FAT32), Windows can’t read or write to Linux file systems (Ext2 and Ext3).
Sure, if you need to access your files from both operating systems you could just save everything to a Windows-readable partition. But even when I tried doing that, I found there would be the occasional file I quickly saved to the desktop and forgot to transfer. Whatever the reason, there’s always some time when you may need files on your Linux file system, but don’t want to take the time to reboot into Linux just to get to the file.