I understand what you're saying now. That's an indirect and tentative benefit, which needs to be stacked up against the immediate and obvious detriment of threads being littered with rote, obvious disagreements. Most especially important to be aware of: even good comments are routinely downvoted! But those downvotes are almost always rapidly swamped by upvotes. In the system you're implying, we'd be reading rote meta commentary for all those fluctuations.
I think the system we have now works well for the thing it's designed to improve.