We, humans, tend to follow our like-minded peers and respond to authority. While that serves us great in many places, evaluating ideas is not one of them.
We don't want to think positive or negative of an idea, because we like or dislike its creator. And we don't want you to celebrate too much, just because it's your leader's idea.
All ideas are anonymous, so we remove the bias towards the creator of it and focus 100% on the idea itself when we respond to it.
Also, solving hard challenges is all about leaving your ego at the door.
So, you don't mind, do you? :)