The file locking approach is one used by centralized version control systems, and are mostly used in the everybody commits directly to trunk style of development. In those environments merging isn't much of a thing. (Of course this style also comes with other challenges, especially around code review, as it means either people are constantly commit unreviewed code, or you develop some other system to pre-review code, which can slow down the speed of checking things in.)

This approach is actually fairly desirable for assets types that cannot be easily merged, like images, sounds, videos, etc. You seldom actually want multiple people working on any one file of those at the same time, as one or the other of their work will either be wasted or have to be re-done.