I think it's a fair ask to have downvoters explain why they have downvoted. Even when we look at Facebook, they also do not have the "dislike" button which many people are asking for. Why? First, nobody likes to receive negativity/reprimands, especially in the public. Second, there are many online trolls who just do negative stuff for the fun of it.

Here on Steem, we have the downvote system and we should take it positively. If you do not like something, at least help the author improve by leaving a note