Comments are meant to help the original poster to refine a question or an answer.
If a poster listens to this advice or criticism and does edit post, the quality of the post is thought to improve. Sometimes, if not often, it does improve.
Meanwhile, the voting train has already left the platform and even if grave problems in the post were addressed or even resolved, many voters do not return to question.
Voting is completely unrestricted, without any real guidelines. The above suggestion would do nothing to people that just "made up their mind" or came only here because something was featured on the Hot Network Questions list (if this would be an internal site-only feature).
Without a feature like this, some vital parts of the raison d'etre of comments and edits is severely hampered.
There appears to be a conscious decision on this explicit feature request for StackExchange already. But that SE design decision was a while ago. Having a picture of H:SE position of this may document our need/want or collective disinterest in this feature to the SE devselopers.