Why don't motorcycles have varijet carbs?

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.

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.