This is mostly due to the procedural "recipe" style programming paradigm that most developers seem to default to. It doesn't scale well past small programs with

This is mostly due to the procedural "recipe" style programming paradigm that most developers seem to default to. It doesn't scale well past small programs with the control flow being embedded in the code so the only good way to follow the flow is to track things through the callers. This is one of the reasons I prefer dataflow programming styles that makes the control flow explicit.