I can’t speak for the other Authors on this site, but I started writing on Lit after deciding to write about an experience that I had in my youth:I’m 100% convinced that the vast majority of the “true” stories on those sites are often written by dudes fantasizing… those stories are absolutely too ridiculous and less believable than the fiction on Literotica. I think those forums in fact encourage it by having a “don’t doubt veracity without proof” policy.
https://www.literotica.com/s/introduction-to-the-lifestyle
Since getting positive feedback and encouragement to continue, my next story was also a true story. Since then I have written over 57 stories, half of which are true.
Btw, I’ve posted “proof” as you asked by posting pics of my wife and exes in the forum section.