There are three things in this forum, and in mankind, that are completely messed up.
First: images.
To highlight my argumentation I want to present books, in general, as evidence. Books as a mass media allows the reader to delve into a universe filled with descriptions, allowing the reader to imagine their own universe based on these facts. This is what books make so interesting and this is also why, everybody who saw a movie based on the book AND read the book things that the book is superior. The movie wasn't based on their imagination and thus think it isn't the best way.
In short concepts the opposite comes into effect. From the short lore or descriptions you almost cannot deliver a full image from a champion. The reader will see a wall of text and have to read throught everything without knowing what they can expect. Additionally images are highlighted in the board giving the concept an advantage against concepts without images. If the image looks interesting enough people are more likely driven to look into the actual concept.
This whole concept of gaining attention is the biggest problem of these forums.
When some posts don't get attention they needed while others get attention they don't need because the only difference is the fact they have images to highlight in the overview it is just plain unfair that the images are displayed in the first place. On the other hand when every post would require an image the value of the image itself becomes redundant and only gets reduced to a graphical hint to the post itself. This is also the reason, I assume, why Riot let images display in the first place.
Secondly: Quality itself.
Most of the following is my own theory and I doesn't have any studies to rely on.
People need to feel some kind of dominance from time to time. Forums are an excellent example to see this behaviour.
When readers encounter a bad concept they are more likely to comment on that because they can distribute their dominance on that concept and the author behind it. On the other hand when they see a high quality post they are mostly intimidated by it. The concept creates dominance against the reader. Thus the reader feels uncomfortable reading it and are more likely to turn away during the reading.
Thirdly: Red posts and "Post of the Day"
This is the worst category of all. And Twitter is a genuine example of that, too. People want to read stuff of people they like. It doesn't even matter if the stuff is related to the reason why they liked them in the first place. Honestly, I couldn't care less about what George Clooney ate for lunch. Not to mention that I don't care at all about actors and alike. The movies they play in are the interesting objects. The persons behind that also humans who want to live their live as we do.
And now we come back to the real problem... the post of the day. Yesterday another concept was Post of the Day. To my resentment that concept was part of two contests currently hold in this very board. Without looking at the quality of the post itself it receive 50 comments and over 1k views. Just because it was flagged as something to look at by unknown people. I don't know if that will influence the judges but still I think it is unfair for every other contestant, not only because I'm one myself.
Honstely, and I maybe would be alone on that point, I would've deleted my post if it would be Post of the Day. I wouldn't feel comfortable with the fact that I would've an advantage against other contestants only because I was highlighted.
Hope this helps a bit.
Zanryu