I've wondered this myself. The aftertaste on some of them is vile. The disappointing thing is that so many products use them when they reduce sugar, but sometimes I just want a reduced sugar product without any additional sweeteners. That seems hard to find these days.
I've been curious about the just-less-sugar idea myself. Like how would a Coca-Cola "dry" taste? Maybe the fact that nobody is offering this just means it doesn't taste good.