hi fi headphones and volume controller pods

what the deal with hi fi headphones not having volume controller pods? I have a set of hi fi headphones and wanted to add a volume controller for convenience, but whats the deal with people saying they wont be hi fi anymore, what kind of loss do we have any how bad is it? what if i added a controller from one of my broken headphones? I mean its just a knob, what else is involved that everyone is so against it?

lol...ya I'm not.

the headphones are 60ohms. volume control is out of a smaller headphone set. maybe 30ohm headphones
connected in the middle of the line.