Some things are done out of an outward image of respectability, Freedom of speech has limits (try talking about holocaust revisionism in Germany for an example. Another fun fact: China has freedom of speech in their constitution).
Keep in mind that on Reddit, even after jailbait was banned, the other subs (chestbait and such) ran for a long time after. Eventually I think there might be enough pressure to kill these on Voat, but for right now, there's enough other stuff for them to worry about in just keeping the site running. As long as all the other subs grow and subs like this get lost in /v/all, I think stuff like this will be safe.
It will go away at some point though.