why don't Y.A make changing category after posting a question possible?

People would cheat the point system and it really would not help. For example, you post for a day in one category and switch it to another for the second day. That is the equivalent of asking two questions so they want their points for that. Just post it again to begin with, it only costs two points in the end. Besides, if you switched the category, your question would wind up deep in the list and would not be seen by many. Last, such a system would not be easy to program. The staff do not need more things to make glitchy.