Because then you would have roughly 50 thousand things for the CM's to bring up in the weekly meeting which would lead to poor time management and really long meetings.
This in turn would lead to the Dev's changing the format of the meeting to an all out CM nerf blaster slaughter fest.
And we love our CM's we can't have that.
On a further more serious note if you treat one kid like they are special eventually you have to treat them all that way. A public promise to a player that their thought/idea/gimmick/ect will be brought up in the meeting could spark a massive community out cry for any number of reasons.
Commenting that an idea will be brought up in the meeting wouldn't increase the ideas they bring up in the meeting. Except for if people new idea were actually being taken into account there would be more of them.
Responding to a player saying that something was an interesting idea or that they are going to bring a topic up in a meeting doesn't make someone special. It does make there point or idea special though. As for massive outcry because of a CM mentioning something to the Dev that amuses me because the CM's don't decide what goes into the game.
Really I would just like blue to be more active in the forums.