Why only one outcome scores
A wheel with four good outcomes would be a slot machine, and slot machines are boring to watch because nothing is ever at risk. Here, three of the four outcomes move numbers around without putting a single ball in a silo, and only the drop converts a stash into progress.
That creates the tension the format lives on. A team with an enormous multiplied stash has, in a real sense, achieved nothing yet. They are ahead on paper and one bust away from being back where they started, and the viewer knows it because the stash number is on screen.
The forced drop at the cap is the safety valve. Without it, an unlucky sequence could leave a match spinning indefinitely with nothing ever entering a silo. With it, every match is guaranteed to keep making progress even at its most chaotic.

