[millstone]

Well I gave 5 reasons up at the top :)

But from a philosophical perspective, referential transparency is a big one. We should prefer to make functions referentially transparent, because it makes them easier to reason about. Sometimes we do not, because it would be too slow or too awkward. But in this case, the loss is gratuitous.

Or to put it concretely: in Python (and every other language), we have the fact that `dict.keys() == dict.keys()`. In Go, this is true sometimes. Doesn't that seem weird to you?