True enough!

I was trying to distinguish keys that I populate with initial values (mostly stock indexes) versus those where I just read values from a user-supplied file. When I populate the index values, I'd like to preserve the case I initially used. When I use user-supplied values, I don't know that the first value I use to populate the defaultdict has any more meaning that the last one I see.

It would just be a nice-to-have feature for which I have a real use case. It's not so critical that I can't work around it.