I think it speaks to people's desire for a quick and easy to set up basic GUI creator with an editor that allows inline code editing, and no need to deal explicitly with the client server interaction.

I myself, as someone who likes to create really solid and maintainable tools, have fallen into the notebook trap and written things like "change the month in cell 22 then execute cells 1 through 3 and 20 through 27 to update the report".

The notebook format was great for prototyping what was really a small app. You don't really have those problems when you're just generating a document.