Multiple inheritance in C++ is a can of worms, unless you're prepared to deal with the related issues of virtual base classes, and diamond inheritance.

That is why after C++ all the languages that support multiple inheritance do so only at the interface level and not implementation code, or rather go with a mix-ins approach.

And in regards to Microsoft world, well the same developers that weren't happy with VCL and Pascal, and in for a treat given that the only modern way to do native Windows UIs in Microsoft world is via .NET consuming DLLs/COM/WinRT, unless they want to either stick with MFC, or the outdated tooling in C++/WinRT.