Because C++ without exceptions is not C++, and those languages cannot catch exceptions, nor call overloaded functions, nor delete or create objects using new and delete, nor refer to fields with classes, nor call methods on objects.
Write exception-free external APIs. It's not that hard.
> call overloaded functions
Write an API that doesn't overload functions?
> nor delete or create objects using new and delete
Write an API around that. You'd need to do it in C anyway.
> nor refer to fields with classes
What?
> call methods on objects
If you can call a function, you can call a method.
Your complaint is basically "you cannot write C++ in Python". Duh.
Maybe it is a complaint, but it's still a fact of life: your code is not reusable without wrapping it in C.
The reality is that C++ is not as reusable as C is: ever wonder why there are so few reused libraries written in C++, while they are so many in C?
Look on your system now - it's filled with C libraries, while the C++ libraries are probably a rounding error.