We give special privileges to members who are the most active. Because they spend a lot of time here, we offer them the ability to do things other members can not do. What you are suggesting is to essentially take that away. What would you replace it with?
In addition, what you suggest lends itself heavily to people coming here, making a topic to promote something off-site/spam projects, and then leaving. We wish to encourage discussion and activity, and the alternative you suggest defeats that goal.