Does anyone mix to mono just to hear instruments in the center?

Interesting oldhvy, I'd be up for demo-ing that, although part of the enjoyment of two-channel listening, for me, is based on the characteristics of the "phantom image" and, when implemented ideally, the magic that takes place between two speakers. 

A little different, maybe off subject.. BUT

Trinaural processor, is why James B did it.. he was a good musician, and the reason for the analog center speaker, idea.. That’s what he told me. Something was missing? Maybe!
He said, I’d have to train myself to listen to a WHOLE new way of sound reproduction.
The way it was meant to be (according to him).. Pretty serious Jazz keyboard guy.. Heck of an amp designer...Ampzilla....

I liked it with a couple of VMPS Planar setups.. very VERY nice..  He did a "live" playback with Brian C of VMPS..
live, recorded, and played back, all the same evening..Amazing reproduction...

Regards..

I've seen "mixing" controls where the knob starts at 6:00 and rotates clockwise. As it does, it slowly collapses the stereo soundstage until, at 12:00, it is mono. Keep rotating clockwise and it ultimately reverses channel content when it reaches 6:00 again. Pretty cool but, obviously, not "pure high end" enough for our crowd.  

Were Beatles vocals not originally center mic’d? Maybe I’ve only listened to remastered albums but I feel like Beatles vocals are always at the center of the soundstage. 

I haven''t but I been known to have swapped channels or remixed tracks due to hearing differences in each ear. The  BRG used to put most old Beatles vocals in the center.