While often called the dismal science, economics is a social science at the end of the day. Social sciences don't have absolute truths and thus require debate and discussion.
I thus feel that by not allowing discussion questions, we are doing two things.
1) We are boxing people into ask questions about economics modeling in or derivations of neoclassical models which are generally quite maths intensive. [This can also enforce neoclassical economics as the dominant school of thought through positive feedback loops]
2) Because of the above, the site can never truly "grow" as the answers to the above topics are generally "texbook" answers and the site will ultimately lack the questions required to attract top economists.