"multiple reasons why tube sound better? It probably is due to how harmonics are handled. Don't tubes impact harmonics differently, ie, provide more emphasis throughout the harmonic range in ways solid state does not? This is possibly why tube's provide a Fuller sound at lower volume."
This falls a bit short of "multiple reasons".
Anyway, to answer your rhetorical question - no, tubes don't "provide more emphasis throughout the harmonic range in ways solid state does not".
Tube power amplifiers tend to have higher levels of musically consonant harmonic distortion than SS amps do. However, that is a broad generalisation which I only mention in the context of your statement/question. It is unwise to attribute a sonic character to any particular technology because there are far too many variables involved in sound reproduction to distill them down to any particular technology.
Regarding the marketplace, SS amplifiers are more successful because they run cooler, do not have fragile output devices and are generally cheaper per watt than tube amplifiers - especially where high power outputs are required.
