It comes with a balance knob?!?! I'll take it!

Typically the better the equipment the less adjustments there are as each has a negative sonic impact. Balance is something nearly all high end equipment has. As @erik_squires pointed out the speakers could have on confined space on one side and open on another, so to have the soundstage centered balance control is needed. Also for people with differential hearing. That is the only control on audiophile gear… the designs to put sound quality first will not have tone controls.

I think all Lamm pre-amplifiers come with "balance" adjustment, in the form of a volume knob for the left channel, and a completely separate volume knob for the right channel. 

My old pre had one, my new one does not.

Interesting, when I had one, and utilized it, (rarely), I did so to figure out what was wrong with my set-up, in order to sound correct back to 'equal'. Well, now I don't have one, but really do the same. Set-up, set-up, cables, a speck of dust on the stylus, whatever, is usually the problem.

That said, yes, I have known those that had a set-up that really couldn't be changed for one reason or another, and in their case, they used it to 'balance' their imbalanced set-up or more importantly, room. So, for those instances it is probably nice to have.

I find it difficult as heck to find a balance control on a PC.

Does that make it audiophile grade??

I had an ARC Reference 1 and Reference 3, both of which had balance controls. Despite symmetrical set up, the sound in my room pulls slightly to the left. The balance control worked exactly as it should and was very useful.