Most artistic content is, in fact, permitted on FA; all we ask is that you rate it correctly so that users who either should not be viewing it for legal reasons, or who don't want to view it, don't have to see it. Whether they could find the same or similar (or "worse") content elsewhere isn't relevant - showing adult art to minors is a legal liability, and trying to show it to individuals who're of age but have chosen not to see it is frankly disrespectful.
Metaphor time!
Let's say you don't like maple syrup (adult art). You like pancakes (furry art), but maple syrup just makes your lips curl. So you go to your favorite pancake house (furry art site) to get yourself a stack of pancakes without syrup (clean art). You look forward to your pancakes, but alas! You happened to come in during Susan's shift, and Susan is a waitress (artist) who doesn't think it should be a big deal if you get some maple syrup on your plain pancakes. Surely you've tasted syrup before, so how bad could it be? So Susan decides she's going to pour a bunch of maple syrup all over the plain pancakes you ordered, because who are you to say your pancakes should come without syrup?
Would you be upset with Susan? I sure would. She decided that her opinion on maple syrup on pancakes was more important than her customer's (viewer) tastes. That's not her decision to make, and if it turns out the customer is actually allergic to maple syrup (a minor), the entire pancake house could be legally liable.
A lot of the people who do draw NSFW will do SFW stuff too. Just no one really asks them for it xD
More people than you think, actually. I've not done any adult commission work in ages, because all I get asked for is clean stuff. Which is fine by me; I don't much care either way.
Honestly, the best ways to get viewers is to make sure your art thumbnails well. If the thumbnail makes people want to click to get a closer look, you've managed to draw them in. Art that visibly tells a story tends to do better, as well. (I'm basing this on stats from my own accounts, primarily my comic account.)