I had a preamp with dual volume controls once and it drove me nuts making the two channels match. Not that I was unable to do it, just that I always had the nagging feeling that I didn't have it right. A little bit of psychology and audio nervosa in play there. While it's true that there's more flexibility, the process of adjustment, listening, further adjustment every time I sat down to listen is not tenable to my expectations of instant audio gratification lifestyle.
If the dual volume controls are stepped attenuators then I'm ok, but a smooth continuous knob made me batty.