Most fan writers don't realize being a BNF doesn't usually translate well to actual sales of original works. Sure, a few make the jump and do really well. Most of us can count on a few sales from our fanbase (say 1 or 2 copies for every 100 die hard "read anything" fans) but expecting a system like Patreon or the like for non-fandom stuff to do well solely on the basis of being popular in a huge fandom doesn't make a whole lot of sense, especially if they aren't already established outside of fandom.