I am an unapologetic and proud fan fiction and real person fiction (= "RPF") writer:
Q: Why do you write mostly fan-fiction and crossovers?
Lawrence Lessig gives many good reasons for remixing in his book Remix: Making Art and Commerce Thrive in the Hybrid Economy which I have read and enjoyed. Writing fan-fiction and crossovers, whether in fiction or in non-fiction (see some of my crossover essays) is the writing equivalent of what he describes being primarily done with music and videos.
Our aversion towards fan fiction and an insistence on "originality" is mostly a 20th century fad, that is slowly (for some values of "slowly") diminishing.
Anyway, the various fiction franchises and idea systems that influenced me are a large part of me, and I cannot throw them away when writing my own works. I don’t have a lot of control of the ideas I come up with, but I know I must materialise them eventually.
Q: What about your real person fiction?
I feature or reference several celebrities in my stories (whether past or present) as a way of Real person fiction. According to the Wikipedia page, such fiction is likely to be legal if it is done in mostly good taste, which I believe and hope is the case for me.
The general consensus is that a celebrity generally allows himself or herself to be a subject of reuse in literature, and that includes me, Shlomi Fish.
Update (2 November 2019): I have now written a more comprehensive essay about why writing real person fan fiction is good.
Update (26 November 2019): I now realise that fan fiction and especially real person fiction can be used to help combat the flood of new characters and names that plagues many more "original" stories. People generally have a rough concept of what characters such as Chuck Norris, Emma Watson, Richard Stallman, Moses, or Miss Piggy, are like and generally can better remember them because they thought about them a lot.
Why I will continue to write my real person fan fiction (fanfic)
There has been a lot of fan fiction and real person fiction in the Hebrew Bible and among ancient Greek and Roman philosophers. For example, Plato's dialogues with his mentor, Socrates are clearly RPF. So were some of the stories that the Israelite nevi'im (mistranslated as "prophets") told about their contemporary or past men and women, whether positively - or often negatively.
If we look at present time, then the Muppets and Sesame Street franchises often invite real life guests as fictionalised versions of themselves to the show, to interact with the muppets. Parodies are also considered fan fiction and some parodies like Spaceballs or Last Action Hero (which also sports some real person fiction) are among my favourite films.
Moreover, fan fiction and especially real person fiction can be used to help combat the problem of the flood of new names and characters that plagues many stories that are more "original". People generally have a rough concept of what characters such as Chuck Norris, Emma Watson, Richard Stallman, Moses, or Miss Piggy, are like and generally can better remember them because they thought about them a lot.