In my experience Reddit moderators do this, not Reddit.
For some reason heavy handed moderation is now the norm across every medium-large sized subreddit. I don't know if it's a cultural thing, there's some top-down pressure, or the nature of the kinds of people who become (and stay) mods.
But I'm finding it more and more the case where mods feel the need to heavily regulate conversations/posting preemptively based on arbitrary personal worldview on what is 'good' content for the subreddit, instead of coming in to help when there's actual problems and situations where downvoting simply isn't enough.
Facebook and Twitter went down this road hard too, but at least they weren't doing it via "community leadership" but instead via the predictable slippery slope of centralized content controls.
Who knows maybe I'm spoiled by HN or naively expect large scaled up organizations/systems to stay as functional as they were when they were smaller. But I don't think it's always a lost cause, many big organizations have maintained high quality - given proper management and push-back against the negative forces which cripple large companies (such as becoming extremely risk adverse).