Source Control is a way for developers to manage their source code. All code in a company of any size should be under source control. However, the choice of the source control protocol used determines the level of freedom/control available to developers and source code managers.
Native filesystems offer some minor form of version control, but advanced systems offer much greater control over the versions and how they can be retrieved.
Even legacy systems have always been developed using some form of source control, be it CVS, Mercurial or Git.