I, like many people, am a huge J.S. Bach fan. I practice at least one of his pieces every time I sit down to practice the piano. I love contrapuntal music, from whatever era.
How many instruments can create a polyphonic texture all on their own? A couple.
How many can do it with more than 2 independent melodic layers?
It often puzzles me as to why more jazz pianists don't use their left hand in any other sort of way than in a "'comping" one. For all of the re-appreciation of pre be-bop era piano players that has been happening since the Marsalis movement, there are not many pianists who improvise and use the left hand for more than chordal accompaniment or the odd touch of a bass note or open fifth.
Pianists like Marcus Roberts, Eric Reed and Kenny Kirkland were obviously know/knew very well educated about 'stride', 'boogie-woogie' and other early piano styles. However unless they are playing some sort of direct reference to that music, i.e. playing a piece written in that era or directly derivative of that style, that don't seem to take on-board the idea of polyphony that is suggested, often explicitly, in that music.
Brad Mehldau is the obvious exception. Now there's a guy who can, and does, play equally well with both hands. Craig Taborn is someone else who comes to mind, but how many others are addressing this stagantion that seems to be happening in the history of jazz piano?!
I would argue Keith Jarrett only ever explores polyphony in a serious way (and boy does it get serious: Dark Intervals anyone?) in a solo context. His trios, even his early, wilder ones, are still very much derivative of that post-impressionist/Bill Evans lineage.
If you listen to Herbie Nichols (check out his solo on "The Third World"), Horace Silver (he's always playing those 3rds and 7ths like little counter-melodies), Ahmad Jamal, Andrew Hill or any other pianists who were intent of creating their own sound outside of that Bill Evans-Herbie Hancock-McCoy Tyner lineage you can here they have carried on Art Tatum/Bud Powell's conception of the LH as both an accompanying and melodic force.
Maybe one explanation is that, with the advent of formal jazz education, it became more necassary to teach a rigid 'system' piano voicings. The set of voicings developed and adapted by Evans, Hancock and Tyner are, in most ways, alot more categorizable, and therefore learnable/teachable, than the more abstract explorations than those other pianists I have mentioned. It is easy to learn voicings: 3/5/6/9 or 3/5/7/9 by rote and use them almost immediately in everyday jazz gigs, therby becoming a perfectly passable jazz pianist who sounds like a jazz pianist.
Tradition is also the main force behind this, but that is no excuse to never push to have the role of the left hand evolve, surely!
Personally I think it is up to the many pianists of my generation who are not mixed-up in the factional dealings of jazz in the late 80's-90's, but who also have a solid understanding of and interesting in early jazz, and other kinds of music that utilise the full potential of the piano. It is our job now to make it work.
Jazz piano rant: over.