The issue is that when you get into complex logic and number crunching, it quickly becomes unwieldy. It is much easier to represent logic or mathematics in a flat textual format, especially if you are working in something like K. A single keystroke contains much more information than having to click around on options, create blocks, and connect the blocks. Even in a well-designed interface.
Tools have specific purposes and strengths. Use the right tool for the right job. Some kind of hybrid approach works in a lot of use cases. Sometimes visual scripting is great as an embedded DSL; and sometimes you just need all of the great benefits of high-bandwidth keyboard text entry.