New technologies are always replacing existing ones. A common transition right now is from C++ to C#. Microsoft helped this transition greatly by creating the managed extensions to C++, which essentially gives us access to all things .NET.
Interfaces are not a language feature of native C++. There are several mechanisms for replicating the functionality, but it's not built in. Interfaces in C#, however, are ingrained directly in the language and are a important construct for any reasonably complicated architecture.