1) Oft same-gender character couples and intimate details in m/f genre books/series. Alnea Alder's Bewitched series and Nalini Singh's recent books, to name a few. Different reader groups.
2) Profanity / Crude language gal..ore... Human or otherwise.
Every normal human act has a sexual connotation... crudity isn't necessary for good writing or humour. Lost the dictionary ?
3) Fetishes, O-sex, Socially pressured Dating / Promiscuity. Everyone has sex... and premarital kinky sex at that.
Even people who are from restrained societies, human or other. The non-promiscuous people have to compromise and be rarin' to go, but RARELY the other way around. No worries of STDs / worms / residual dna / cleanliness / privacy / preferences. Romance = Sincere Feelings, not sex manual. That's what the erotica genre is for...
4) Tattoos, Leather / Minimal Clothes, Loose long hair. Impractical in people who are always expecting to fight and get injured.
And, Tats traditionally have specific cultural reasons not merely ornamental hodge podge.
5) Bad people as heroes (m/f). All is forgiven as long they're : good looking / sexual athletes / "true love". Doesn't matter if they're rapists / mass murderers / torturers / perverts / supporters of rapists-murderers-perverts-invaders...
6) Multiple Male Partners for Females.
7) Chapters with character name subtitles. Rather pre-schoolish / draft style. Are adult readers suddenly unable to follow a flowing writing style ?