If bi-amping is so great, why do some high end speakers not support it?

Yes, Vandersteen has a white paper.  He was sharing at Audio Connections during one of his visits.  I've spoken very recently with him about bi wiring and I can't share what he said, because I honestly don't remember it, lol.  I do however remember his saying something about the powered speakers don't benefit quite as much as the non powered speakers.  Something about the bass.  I'll try to find out what I can when I'm able to.  

It's a very interesting debate, but honestly, if a designer has designed their speakers to be bi wired and or bi amped, then I don't see how we can say they are wrong.  The bi amping basically is to help with the bass control and that in turn will also free up the upper amp to deal with the speed and control of the mid and lower any problems you may have with dynamics.  It would make sense that is what he's doing with using powered subs in the Quatro on up.  I just switched from Treo to Quatro and it's not just the bass that is better (especially with the 11 band room eq), but everything is so much better.  JMHO

Bi-amping with tone controls using vintage amps, that is where it is at. For around 800USD one can have two Ymaha Class A amps or Luxman Class A running their system. You can adjust treble, mids and bass to get the best out of recording. My speakers are always lacking in bass on Jazz or Hard Rock. One touch of tone control and the bass comes out...
I recently bought wide buffle speakers from Pioneer that are capable of tri-amping (not that I am gonna do it) but just to show that the ideas are very old as Pioneers are from 1970s. I'm lately became drawn to wide baffle sound (JBL, Wilson, Devore) and really come to dislike thin sound of the narrow baffle speakers.

ctsooner - I'll rephrase your comments a bit:

if a renowned audio engineer and speaker designer has designed their speakers to be bi wired and or bi amped, then it is very wise for a consumer to follow their directions

Dick V. is highly respected and has been working towards maximizing SQ in his given designs for decades - it took me months of careful listening for hours every day to decide to move from Vandies to Maggies (and I understand if others make the opposite move)

I submitted an email question on the subject to Richard Vandersteen and he kindly responded. My question was specific to my 2Ci speakers and his response was he no longer recommends bi-amping for model 2s, including new models. No additional explanation was provided.

Bi-amping makes an audible difference in for me. My Carver AL III+ are bi-amped with 375W p/c to the ribbons and 150W p/c to the woofers. Noticeable difference in airiness.  My Klipsch's are bi-amped with 100W p/c to the tweeter and 200W p/c to the midrange (+ powered subs).  I can hear a distinct difference with bi-amping with the Klipsch also. Tried A/B comparisons and bi-amping won out.