It's because they have incredibly strict rules about what can be posted. Only certain news articles, from lefty .. I mean trustworthy sources, they require you to link a ton of alternative sources, it has to be checked for any remotely right wing thinking, etc. Go try to make a post. See what happens.

It's a god damn joke, but unless bots have perfected impersonating soy boys and gender fluid panumptibians, there's a lot of people posting there.