Why do most engines have 1 timing belt sprocket and a camshaft chain, instead of 2 timing belt sprockets directly driven by the timing belt for the camshafts?

Question

I might be in the wrong, but in my limited experience, most modern engines (inline 4) seem to have 1 timing belt sprocket which is run by the “dry” belt, and then a “wet” camshaft timing chain to link the 2 camshafts for timing of the valves.
Does this not introduce more complexity, as well as another point of potential failure?

Why have engine manufacturers stepped away from having 2 timing belt sprockets, one on each camshaft to be directly run by the belt and thus, not putting a wet chain between the two camshafts in the top end?

In: Engineering