That's true, this is the example that most people will run into in practice. But the print example is useful because it shows what's going on more explicitly: t

That's true, this is the example that most people will run into in practice. But the print example is useful because it shows what's going on more explicitly: the default argument gets evaluated as part of the function's definition. I think this helps people get a better intuition for how Python's interpreter works when it comes to evaluating function definitions.