So you can see the opposing side; why your view is disagreed on, to open the other side and with that, you can explain exactly why you're correct. For example, Ice cream shouldn't be eaten everyday. People might say that ice cream is good, and if you eat low-fat it would be better. But with that, ice cream as a whole tends to be unhealthy due to the sugar content, and overall it was designed as a treat.
It enhancesyour view, because if you just say why you're right, it won't exactly be as creditable.
