It's pretty much necessary for projects with multiple people to prevent conflicts and such. But even with a single person, it helps with finding bugs, keeping track of changes, and if need be, rolling back to an older version because you liked it better. It's also very good with mods, as mods are generally version specific, and some people may be interested in having access to older versions.
I find the main problem with most version systems, especially for independent developers, is they are too clunky and fancy for simple use, and get tedious. It's why I have been looking for something new lately; SVN is a pain when working alone, Git is better, but still somewhat excessive. I'm looking at trying Fossil, and if that doesn't work out, I'll just write my own simple system, not like I need full sharing support.