Why don't motorcycles have varijet carbs?

[wheelbender6]

Thru the 80's, V8 powered cars used four barrel carbs - two barrels for normal driving and four barrels for passing power.
The four cylinder Mustang used a varijet 2 barrel carb - One barrel for normal driving and two barrels for passing power.
I don't recall motorcycles ever having varijet carbs (except the BossHoss V8 cycles). They used every venturi all the time. Maybe the motorcycle MPG was already so good that the cost of a varijet carb wasn't justified?
I realize that modern fuel injection has made the varijet carb unecessary, but the question still kind of bugs me.

 

[GearNut]

My 1990 Yamaha XT350 had dual carburetors. One was a CV that acted as the secondary and the other was a variable venturi (slide style like a NT) that was the primary.
For a better look, I found them on an ebay picture http://i.ebayimg.com/00/s/MTIwMFgxN...g/$T2eC16F,!y8E9s2fjE+QBSUH3fDIc!~~60_35.JPG

 

[wheelbender6]

That's a slick carb.
The Honda Interceptor sorta does the same thing a different way. Only 2 valves in the head operate below 7,000 rpm. The second set of valves are actuated above that rpm.