Fair on not knowing what you'll get out of someone. But if that varies wildly, I may not want to hire that person. Even with employment, predictability matters a lot. If they underperform too much, I might feel annoyed. If they overperform, I might feel guilty.

They can charge whatever they want, I think many people like to make business decisions based on relative predictability or at least be more aware that there's a risk. If they want it to be "some weeks you have lots of usage, some weeks less, and it depends on X factors, or even random factors" then people could make a more informed choice. I think now it's basically incredibly vague and that works while it's relatively predictable, and starts to fail when it's not, for those that wanted the implied predictability.