One thing I would definitely use this feature for is making back-up copies of a storygame before I have a proof-reader proof-read it; that way, if the proof-reader accidently or intentionally deletes parts of or the entire storygame, then I haven't actually lost anything and I can simply make another back-up copy of the back-up copy and give the proof-reader another chance or find another proof-reader.
This also applies to co-authors; periodically copy a storygame when you have a co-author on your storygame, and if that co-author accidently or intentionally deletes parts of or the entire storygame, then you haven't lost much and you can continue working on the storygame with the co-author or you can salvage your own work. Of course, this can be done with copying each individual page into a new storygame, but this is tedious, and replicating the potential variables, scripting, and items is even more tedious.