While this looks simple on the surface, what I've found is that there's a missing component to what you describe: the effect sugar has on the perception of satiety: when I eat sugar, I always have a hunger-like feeling, which incites me to keep on eating. I don't get this with sweeteners.

This happens with sugary drinks, but also with solid food, such as cake.

Sure, once you see your weight go up, you can adjust. But adjusting is difficult, and I think this is a contributing factor to the weight problems people have.