Why? Well, consider the scenario where somebody imports your module but it has a bug in it.
We're practically the same person. XD That's one of the use cases I always reach for when talking about Penknife or about language hackability in general.
I still don't really like Python's "everything is open!" approach, but I appreciate it a bit more now than I used to. On the other hand, I do think it's a good fit for Arc.