C++11: why does std::condition_variable use std::unique_lock?

Question

I am a bit confused about the role of std::unique_lock when working with std::condition_variable. As far as I understood the documentation, s

Answer 1

It's essentially an API design decision to make the API as safe as possible by default (with the additional overhead being seen as negligible). By requiring to pass a unique_lock instead of a raw mutex users of the API are directed towards writing correct code (in the presence of exceptions).

In recent years the focus of the C++ language has shifted towards making it safe by default (but still allowing users to shoot themselves into their feet if they want to and try hard enough).