If you come across a question that was posted as a reply to an answer, and that answer contains ten different points, it's difficult to find the specific part that the question was responding to.
Look at the icons on the right of this answer: you can agree with the answer, be unsure about it or disagree with it. A problem arises if you agree with one-half of answer but not the other half. By having only one point per answer, you don't get that problem.