No preamp 'Balance' control?

Most but not in all recordings the singer or main instrument is in the center. If you have a mono switch in your preamp set it to mono, if everything is in the center switch back to stereo and if the singer or instrument is not center that’s way the record was recorded. If everything is not in the center with mono then you definitely have a problem. I have more than a few albums that seem out of balance but that is normal again because they were recorded that way. BTW this seems to be more evident the better the system gets, probably because there is better channel separation especially with vinyl.
Ther are a few threads on this subject here on audiogon.

Balance controls are really tricky to implement, but valuable if done right. Tricky as they can cause degradation of the sound the way a volume control can (loss of detail and bandwidth are the 2 big issues).

OTOH if you don't have one, recordings that are poorly mastered or any weird imbalances in your system including room anomalies will not image right. Generally you only need a few db, but IME those that have really highly resolved systems may only need 1/4 of a db of adjustment, while those with poorly set up systems might need considerably more. So the balance control has to be continuously variable and have a little range, yet somehow not affect the sound.

Our solution was to create a control that varies the *gain* of the circuit rather than the level of the signal going to it. This keeps the control out of the signal path. It also limits the range of the control to about 8db, but allows for the micro adjustments that can really make the difference.

I could not do without a balance control. Many recordings are not balanced properly and most rooms benefit from some adjustment. All of the high end preamps that I've had through the years have had this feature. I also believe that most systems would sound better if premium level componets would include some form of transparent equalization along the lines of the TACT unit. Control is a good thing as long as it doesn't subtract from performance.

I think that most people do not have symetrical dedicated listening rooms so balance controls are necessary for many.

I don't think that fewer parts = better preamp. You don't want unnecessary parts in the signal path but I'm sure there are many preamps with balance controls that sound better than many preamps without them.

My Pass X-1 Pre has dual volume controls that are turned up simultaneously, and you adjust the balance by turning one up or down individually. It works and sounds great. Sometimes I like to sit far off center in my rocking chair and I can still get a really good soundstage.