It's creative freedom.
Back then, game designers could not use much to produce games like they can today, as well as back in a day where the consumers morality was different then it is today would explain a bit. (Even SNES Ad's at the end give a warning that all kids should have their parents help set up the console, what kind of gaming ads do that today?) There was also a big change in regulation. For example, Conkers Bad Fur Day was given a M rating for its references to alcohol, sex, violence, blood, etc. But today, they would have given it a T rating.
IMO, I have no problem with violence or sex in video games. I don't play many games like that but it's not in my power to force people not to play them, neither the governments.