The work was originally posted on Pixiv by the artist and then later re-uploaded here by someone else.
Some artists uses alternative sites to host uncensored versions. Keihh has both a Fanbox and Patreon, it is possible uncensored version of his works are available on those but uploads of paid content are not allowed on Danbooru.
True, this is Danbooru. And Danbooru is a repository for pictures, whether they're from Pixiv, Deviantart, Twitter, or even Hentai-Foundry, so absolutely nobody will draw something exclusively for Danbooru, first because it's not what Danbooru's for, but also because there's Danbooru, Gelbooru, Sankaku Complex, and so on. My point is that Danbooru is nothing special, so it get whatever is posted elsewhere.