I think I agree with what people were saying about the "vibes" in each section. I've participated in mostly Casual RP with some Advanced, and I'd say that there is a distinct feel to each of the categories, whether it be through their writing style or OOCs. GMs may not be looking for people of a certain caliber but rather those who carry a certain approach towards RPing.

I'd also like to bring up the fact that there are "cliques" (groups? friend circles?) of RPers that may have met in one section and just continued to have all of their RPs in that section, regardless of if that new RP fits the section. This isn't the primary reason why, but I do think it's a contributing factor.