[iguessthislldo]

The actual "why" is the author did it for fun, there's basically no purpose to it. I can try to explain it though:

Interacting with file systems can be generally summed up in a handful of basic operations. Two of the most important operations are open, which asks the filesystem if it has a file of a given name, and read, which reads the contents of that file. FUSE is a Linux wrapper for writing virtual file systems by implementing these basic operations. Here open, instead of taking a filename, is telling the program what command to run and read, instead of returning the contents of a file is returning the output of the command.