Default values for keywords are saved as part of the function signature itself, at function definition time.

Without this it’s not clear how you’d introspect the default kwarg values of a function? Would they be computed every time the function is inspected? If they are lazy then what if the default value is expensive to compute or has side effects?

So I would not say it’s a horrendous decision, it’s a clear trade off that IMO fits quite well in the Python ethos - everything is an object, and everything can be introspected.