Erotica is a form of fantasy, and some people do read it for escape, so in that case the safer sex discussion might not be completely necessary.
Erotica does not always equate to erotic *romance*, where there's sometimes an assumption that characters are going to behave more in line with real-life human beings. In some cases, erotica is the fantasy of sex, while erotic romance is the fantasy of *romance*, which for some (authors, readers, publishers) includes the respect and consideration between partners that is sometimes demonstrated by practicing or at least discussing safer sex.
I'm like Lori; I don't include safer sex or the discussion thereof as a public service; I do it because I feel to do otherwise would be a *disservice* to me as a person and an author. It's what *I* feel right writing. Not for the readers, but because I had friends who died of AIDS and hepatitis contracted from unsafe sex, and I want to have my characters not do that.
I did have one story in which the heroine got pregnant, though; the hero was a werewolf and said, "Well, werewolves don't carry diseases and can't contract them, so we don't need condoms"; neither considered the possibility of pregnancy because in that universe, female werewolves can't carry pregnancies to term and so the hero just plain didn't think that he was fucking a *human*, who could get and stay pregnant.