Alas, it was basically because there was too much controversy in there and too many people getting mean with one another. I miss them a lot. Now you can only read them, and you can't add comments to them either. Hope this helps, good luck to you.
Why Did Blurtit Cancel Debates?
This was started as a Q&A site and they decided that the debates just didn't suite the purpose of the site and the arguments that got started there didn't help