Why no index to indicate proper listening level?

I recall that a well respected engineer said that there was only one correct listening level for any given recording. I believe that aside from the people who favour smallish bookshelf speakers fed by a high quality low power amp and therefore, through choice or need, stick to polite levels, the point of an audiophile quality system is to faithfully reproduce the musical event. This, invariably, means that the music gets to be loud at times, either because of the dynamics involved (such as orchestral music) or simply because modern amplified live events are loud all the time. Why is there not some kind of standardized reference built-in to a recording (would probably be quite simple with digital) indicating what is the optimal and realistic level at which the recording would sound right? This would certainly separate the grain from the chaff system-wise. I am certain that a lot of highly touted systems (at least by the salons selling them), mostly British but not all, that are demoed at such polite levels that a crescendo is the only thing waking the listener up from his stupor, would run out of breath real quick. On the other hand, Godzilla like classical guitars would be avoided. My question then, why no standardized level when somehow people fret over stereo imaging and timbre, that can only vary in accordance with the volume level, not to mention distortion and hard clipping.