The calculation is likely that users do not participate as much if you increase the cognitive friction involved in performing an action. Having to select an explanation for the vote is absolutely a much heftier problem than just expressing the sentiment.
The issue is probably less in the interface presented to users and more in the way the backend accounts/tallies scores, and then uses that data to determine the placement of the content.
The "direct democracy" approach of just taking the raw counts and sending them through a pre-set formula results in groupthink and echo chambers, we know that. As you know, Slashdot's saving grace was not that they required posters to say "Insightful!", but that there was reasonable human curation supervising the system.
Reddit takes a laissez-faire approach to moderating content, leaving it in the hands of subreddit moderators, and afaik does not attempt to modify non-spam vote counts (except for a few exceptional subreddits).
While you could definitely write more objective algorithms for ranking content, the question is really "Content is better according to whom?" Because the fact is that most people do not want to hear from the other side. You will not have a successful community where one story is "Vote for Trump" and another is "Vote for Clinton". You will have factions that try to tear each other apart (reddit is also an example of this, but not because the ranking is trying to be fair).
Not only do most people not want to be "open-minded", aka "experience and suppress cognitive dissonance until it's rationally justified", most people are frankly incapable of doing so. They do not subscribe to the FB pages of both Local Dems and Local Reps because they like to know both sides of the issue. They subscribe to one or the other, or neither, because they've selected a tribe and completely intend to stay with it. Information contradicting or deriding their tribe is a vexation, and they won't tolerate it.
The implication for content ranking is that if you want an intelligent ranking system for interesting, challenging, or in-depth discussion, you want something completely different from what the public demands.
And that really gets at the crux of this whole issue. We look at "native ads" promoting fake dating sites, penis enlargement pills, and gambling, and we scoff. These work because many other people don't scoff, they say "Yes, I want sex and money" (and who can really blame them?). While they may be socialized to be embarrassed about it, they take advantage of the privacy the internet offers them and click anyway.
Now the question is, you have a business that has to make money. Like it or not, which market is the better target? The discretionary, measured, judicious reader, or the person who will impulsively click through to a site promising him an elongated penis?