Is soundstage DEPTH a myth?

"About soundstage, I've owned TOTL headphone and I still couldn't notice soundstage. I've clearly sense what's in front of me from front left to front right. I've also heard things up close to my side left and side right. This kinda qualifies as soundstage depth. But when it comes to the front depth, that I haven't clearly heard"

@toddalin I made some obvious errors in my statement. Soundstage and imaging are definitely a thing. With that being said, I don't quite understand your question 

"wouldn't this be expected of headphones where there can be no interference between the channels let alone some predetermined distance between the speakers that the engineer was listening at?"

Are you saying depth is a result of sound bouncing off the physical room? And since there's nothing to bounce with in a headphone, there is no depth? I'm sorry for not understanding. 

@cd318-

Since 99.99% of commercial recordings were made with little or no consideration for sound quality, let alone soundstage depth, it could be considered more than a little irresponsible to advocate upgrading in pursuit of this elusive soundstage depth.

So let's not kid anyone, out of the millions of commercial recordings there's probably less than a 100 that could be said to be of audiophile standard and possessing genuine soundstage depth.

         Could you please cite you sources, for the above figures/information?

       The adherents of the Naysayer Church will never accept that there exist a multitude of variables, when an accurate simulacrum of performers and their performance in a particular venue, is the desire/goal.

        If their result differs from that of others, the aspects that they can't discern CERTAINLY MUST BE the product of those others' imaginations.

             Of this they are certain: it CAN'T be THEIR system or ears!

                                      Perish the thought!

"Are you saying depth is a result of sound bouncing off the physical room? And since there’s nothing to bounce with in a headphone, there is no depth? I’m sorry for not understanding."

Not so much bouncing off of stuff in the room, but the interaction of the sound waves of the two speakers playing simultaneously in the room.

Something to consider. If both speakers play the same thing, in phase, there are constructive as well as destructive interferences (peaks and nulls) set up in the room. For something to be dead center, both speakers are playing the same thing, at teh same volume, in phase, reinforcing each other and sound is therefore louder at that spot. Similarly, depending on the wavelength and distance between the speakers, you could have a path differential that creates a null when both speakers are playing the same thing

But on headphones, the center is in your head and the sound of both channels is not reinforcing a wavefront making it louder, or quietier, if you are listening to a null spot.

Many Classical records made in real hall acoustic environment with small number of microphones have a real soundstage depth. I mean big part of live records (from 1970x - 1990x) and records done from 1955 to 1965.