Of course it will not vape all at once, but how precisely can you get 1 exact dose and not less/more. After finishing inhale it takes some time typicaly 5-30 seconds to kick in. And it needs to kick in with desired intensity, not too weakly (waste) or insanely overwhelming (brainfuck). After waiting and realizing it was not enough it is too late to inhale more, because of paralysis. And without waiting, there's possible overdose. So precisely weighted (mg precision) one-hit loads are key imo for efficiency and safety. I don't have enough balls to inhale from something with 1 gram in it.