Based solely on my previous experience with a "flow-based" programming system, which endeavored to make programming financial decision logic a matter of connecting boxes, it's the 80/20 problem. It makes 80% of the work dirt simple and able to be completed.

The remaining 20% still needs to be implemented in code, and takes most of the time. It got so bad that they actually ended up implementing "code" objects, just so the code could be edited and incorporated into directly into the tool instead of around it.