Originally it was because I was used to how other forums operated. In every other forum I had participated, arguments would break out. Fights where the people would get carried away, off topic, but not caring, as long as they showed that they were "right".
I myself loved to argue and debate. I didn't care what the topic was, I just enjoyed the challenge of arguing.
With that in mind, I thought a section where people who were arguing and taking a thread off topic could be moved. That way the thread stayed on topic, and the people who didn't care about the fight could enjoy the conversation. Yet if the participants in the argument cared to continue it, they could do so in their own section of the forum.
We just haven't had those types of clashes.