I can't think of the last time I used a knob with a mouse; you usually map it to a knob on a MIDI device and the GUI just gives you visual feedback

Really depends on your workflow. Many, many successful musicians are entirely or almost-entirely "in the box" and use mouse+kb for everything. Doubly true when you're talking about mixing and mastering workflows where you're not usually going to be using a MIDI controller at all (but doing plenty of knob-tweaking).