IMO, Nothing has ever competed with ero/romance, even way back in the 70s. And now, If you take amazon stats: The top five more profitable categories on Amazon.com are: Romance/Erotica ($1.44 billion). Crime/Mystery ($728.2 million). Religious/Inspirational ($720 million). Science Fiction/Fantasy ($590.2 million). Horror ($79.6 million). It being more popular is just the norm.