It allows 2 or more people to work on the same program from different locations. 

Back in the cheap seat days we used a Sneaker Network. Work at a different location > Backup data to a memory stick (we used floppy disks) > put on your sneakers and run it to the main computer, where all returns find their final resting place > Restore from the memory stick > Process the return.

Okay Wikipedia is calling it SneakerNet This has no extra cost, but more room for human error in transmitting the wrong copy of a file.