This is for both Nuendo and Cubase.
Here is the scenario -
I want to add a hardware synthesizer into my project. I have to make an input in the Audio connections, create a Midi track and then create an audio track.
I think putting all three under one window makes a lot of sense. You could choose to add the other two if you wanted or just ignore it. My set up always has a lot of audio and midi inputs and tracks. Tis would really speed things up.