Human nature being what it is, the vast majority of us are disinclined to offer half-thought-through, but potentially useful, policy notions only to have them embarrassingly dissected in front of a national television audience. When undertaken in such a medium, deliberations tend toward the less provocative and less useful.
I do not say that such a system cannot function, but I do say that in my three decades in and out of government, I have never seen it function well. The undeniable, though regrettable, fact is that the most effective policymaking is done outside the immediate glare of the press.