Lots of modern (...3+) python code uses type hints and a type checker. It can be as strict as you'd like it to be, which is exactly how I like it. It's what pulled me away from ruby.
Meanwhile, static languages are too often a giant pain in the ass, and in return for writing a lot of annoying code, you get in return guarantees that only really apply within your process's memory. And in a microservices world... you're actually realistically using the protobuf type system. Which generates just fine for python. And then "internally" you can use python's type checking where it helps, and if it doesn't help, then for that bit of the code, simply don't use it (and write "true" python).
I also find that a HUGE problem in the world is that programmers just. can't. help. themselves. They LOVE to over-define. LOVE IT. It's a siren's song!! Static type systems are a trap for the part of our brain that loves to architect. One of my favorite things about python is that it helps programmers _let go_. Not everything needs to be an interface. It's python. Everything is already an interface. Now just write the code without all the distracting 20 layers of indirection. And if we ever need one more, it's python - it's practically already there. Just make a new type, put @property on some methods, and you're good.
Obviously there are times I'd not use python. I could foresee myself writing Rust if I had to do code where correctness was of utmost importance (like, crypto, or embedded software for a medical device where someone's ventilator is hooked up to it, or similar). But if nobody's going to die (so... medical and cryptography...) then I'm using python almost no matter what I'm doing. And I'll use numpy or write a C module if I actually end up needing true CPU-bound performance for something.
That is not the case if you default a value in the function.
`def foo(x=None)`
Of course then you usually have to deal with it in the body of the function even if you didn't need the arg all the time so your point isn't without merit.