I do think we should bring it back, but I had to think about the why for a while.
Part of me just wants it back because I got used to it on reddit, but I do think it has some purpose, such as:
-it makes it feel like your vote counts more, as not doing anything with a bad/unfit post sometimes doesn't feel like enough
-seeing a post or comment downvoted to oblivion shows the opinion of the community better than it just having no upvotes, as that can also be seen as the thing not being seen
-not having the option to downvote could skew peoples judgement on some bad posts, as any post'll get upvotes regardless of how bad it is, and downvotes would balance that a lot better.
I don't know if this is sufficient reason to actually bring it back, but I at least wanted to share my two cents on this matter.