I'd guess due to too many low quality or spammy submissions from there.
The other answer is apparently the reason. It’s a shame, too, because it flags people as self-promoting even if they’re posting interesting articles that have no self promotion at all.
Have a scan through the homepage. I often find the same few people posting broad questions over and over again to generate engagement. On top of that I feel most of the article titles tend to be click bait. I have come across one or two really good articles but they are very much the exception.