How come people ask questions that they can answer themselves?
We have to keep in mind the wide variety of people that are on this forum, along with the wide variety of backgrounds and educations. Some of the people asking questions are young kids. Some of the questions are rhetorical, and some use this as a forum to play and joke. Also, our perceptions can be skewed. Things that seem obvious to us are not always obvious or common knowledge to the next.
