For the less diligent, the wisdom of making regular backups only coalesces once you lose important data in spectacular, unrecoverable fashion. There are a bunch of software options for duplicating and safe-guarding your important information, but what mechanism is best? Usually the domain of software developers, source control software, such as SVN and Git, is well-suited for regular documents and even binaries. So why aren't you using it?
Tobias Günther over at Six Revisions has penned an article covering six "myths" of Git that might stop one from giving it a go -- whether they're a programmer or not -- though the logic applies to any form of source control. For example, the cry of it being too complicated is as applicable to Subversion as it is to Linus Torvalds' creation (for the new user at least), but there are plenty of GUIs and front-ends that take the pain away, especially if you're on Windows.
Why would you use it for backing up files other than source code? It takes away many of the problems regular backing up introduces while providing options you just don't have by straight-up copying. The biggest of these is that you can easily compare documents from any point in their history. Compression is also taken care of automatically, so you don't need to worry about how to store your backups and online services such as GitHub mean you can stow your info online, with private repositories providing security if needed.
The disadvantage is that without the software, the files are basically inaccessible, a problem you don't have with a straight copy. The odds however of not being able to wrangle a Git/SVN client when you need it are negligible, though it could prove a little troublesome with less tech-savvy users who just want to recover their mangled TPS reports.
Like anything, it's one of many backup options available -- it's up to you to decide if it's the best fit for what you're doing. In the case of developers, extending something you're already using on a daily basis to solve a similar issue elsewhere seems like an easy decision.
6 Myths Preventing Developers from Using Git [Six Revisions]