Why does the moderators in Yahoo Answers delete questions without giving a reason?

Actually, when blank, the users that reported you thought it was obvious. Yahoo does not have to give you a reason. If you want to know the reason for the violation, post "Why was this question (answer) a violation?" and add the original e-mail you got so the users can see the exact context. The experienced users here will explain it to you. There is no statute of limitations on breaking the YA rules.