Why are there limitations on yahoo answeres?

They want someone to answer that knows the correct answer. They have to have limitations because there are 13 year olds on here. I answered a physios, question wrong two days ago, and he turned me in. I really thought I gave him a good answer. But, I guess he didn't think so, yahoo sent me a letter and said if it happened again, that they would delete all my accounts. They , also gave me a link to go to argue about my answer, but I didn't go there.The source is below. I hope the source helps you too, and if not , maybe someone will give you a better answer.