Something is puzzling me and I hope the users of "Math Answers" can enlighten me?

This is not a question about math, but a question about you. I enjoy reading the questions posted here and I like to figure out the problems that I find interesting. Sometimes I post my solutions, but I am usually not the first answerer because I like to make sure that my posting is clear and is stated as simply, but thoroughly, as possible. (I also take time to double-check to be certain that it is correct!). I try to post answers that demonstrate that solving math problems doesn't require a lot of memorization or possession of obscure, secret facts, but can be done with correct and expeditious use of the facts the questioners probably already know. In other words, I invest a lot of time forming my postings, and I'm proud of most of them. They are for everyone else who reads and answers the questions, not just the questioners.

However, during the past couple of weeks, over a dozen times I have submitted an answer, only to find that the question has been deleted by the questioner a few minutes after it is answered. This has happened twice already this evening. Why? Do people just want to save the five points that asking costs them? Are teachers checking Answers to catch students who don't do their own homework? I cannot really see a good reason for deleting a legitimate question and its answers after it is posted, and I am discouraged from spending my time composing future solutions. Give me some insight on this. I welcome responses from all who care to comment