Various reasons. I generally always include it if it’s in the community/magazine rules. Sometimes I’m curious if anyone recognizes a show (or cares enough to bother asking) and will leave it out deliberately. (e.g. I did that on my “Normal Girl” X-Ray skull screenshot to !animepics since that one’s pretty obscure and I thought it’d be more fun to post it mysteriously; no one cared enough to comment though.) A lot of posts get no comments at all, and even just getting a “WTF is that from?” question can help with engagement. Sometimes I’m just tired and forget.

In this case, it’s from Kids on the Slope (坂道のアポロン) and I probably should’ve included it in my comment with the bonus images but I was tired when I posted.