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

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. 

Pretty obvious that some folks like it one way and some the other.  As Tomic posted above, the bass and can affect the HF, so it helps to separate them. I have heard my Quatro's wired both ways now as I had some Kimber around that allowed a true bi wire.  I personally don't like the Kimber cables and that's why they were in my trunk.  The point is that when bi wired, it was much better.  The bass was tighter and the HF's were much more coherent.  My wife agreed as did the rest of my family that was visiting.  I don't think they will forgive me for subjecting them to this unscientific observation, lol....