[jstimpfle]

There's a big issue with C++ classes -- or rather methods. You need to list the entire class definition to expose public methods. That includes private members and private methods. This breaks encapsulation, exposing implementation details and their dependencies in the public header. This in turn leads to looong compile times and needless recompilations.

[pjmlp]

Hence modules, and yes I know there are still some issues to sort out.