There are so many reasons for this. Most people have a real job and want to meet friends in the evening, not challengers. Debating someone with your rules in mind that the others didn't learn also feels like slapping someone who's unarmed. It's even less fun on the receiving end. In jobs, there's now something riding on arguments; In academia you just debate the death sentence or the draft and call it a day. At work if you accept this kid of argument and lose, are you expected to spend the next months implementing someone's else's idea you don't like? In any case, most arguments are futile, since the position you're arguing for is kind of arbitrary and pulling arguments out of a hat doesn't really improve them.

This article and your comment really resonates with me. My experience in the philosophy department was almost identical.