looks like a porn

Well that wasn't unusual for the time. Other erotic thrillers released in the same period had the couple doing it on the cover like Jade or Sliver. Hollywood has become so puritan these days despite the MPAA restrictions arguably being at their least effective in years, we ironically don't see these types of movies any more. The closest we've had were the Fifty Shades of Grey movies, and those are like grade school compared to some movies from the 80s and early 90s.