Saving everything into Dropbox is just so incredibly easier than trying to manage and keep track of and not damage an external drive.

Storage is cheap enough these days that each of my computers has more HDD space than I need for my whole Dropbox, so I don't have a need for a "true" external drive. I primarily use it as a backup and secondarily use it to sync across machines. Every file of importance lives in my Dropbox directory, so when I'm working on a project or something I don't even have to think about backups. If my apartment building burned down or all my drives simultaneously died, I wouldn't lose any data. And if I ever need to glance at some file away from home I can always do so.