Windows apps are not the raison d'etre for C++. The windows API was written in C++ BECAUSE C++ has certain capabilities (as does any OO language) that you just flat don't have in non-OO languages such as C. These capabilities are enormuosly useful in creating complex relationships among data and functions and in creating a hierarchy of functionality that is like nothing that exists in non-OO languages.

What do you use it for? Well, it's best used for fairly complex development tasks of any type and it's much less useful for simple one-off utilities, for example.