AFAIK /sites subpath is mostly for articles made by "Forbes Contributors". How does one become one? You need to be invited by one of employees[0], but then it seems you can publish whatever with little editorial oversight[1]. You get paid, starting at $250 a month[2].
Personally, I find the idea nice, but a lot of these contributor articles seem to be poorly written anyways, so I try not to bother with them. But I guess that compared to a lot of other places in modern internet, especially medium.com and a ton of blogspammy wordpress sites, these must still look like Shakespeare in comparison.
Once I noticed the surprisingly consistent, legibly distanced branding, I imagined something -- actually more like contributors paying. Thank you for the research & explanation!