I think it's because of how other people interpret them as normal jokes. Most of these here have stupidly long filenames that rarely work and/or are simple references. The point of these threads, at least in my opinion, is a short and quick joke, which almost always involves a short filename paired with an image specific to it. And I think that's where most people fail. There should be an equal "sharing" of name and image. The image itself needs to be of good enough quality itself to invoke a joke. Too much explanation and it seems forced; too little and no one gets it. And there are also just plain bad ones that simply won't work no matter what.
Then again, I'm just a random anon who has different opinions from others, so whatever.