Actually, George R.R. Martin has said that the books are a reflection of the medieval times

“The books reflect a patriarchal society based on the Middle Ages. The Middle Ages were not a time of sexual egalitarianism. It was very classist, dividing people into three classes. And they had strong ideas about the roles of women. One of the charges against Joan of Arc that got her burned at the stake was that she wore men’s clothing—that was not a small thing. There were, of course, some strong and competent women. It still doesn’t change the nature of the society. And if you look at the books, my heroes and viewpoint characters are all misfits. They’re outliers. They don’t fit the roles society has for them. They’re ‘cripples, bastards, and broken things‘—a dwarf, a fat guy who can’t fight, a bastard, and women who don’t fit comfortably into the roles society has for them (though there are also those who do—like Sansa and Catelyn).”

“I’m writing about war, which what almost all epic fantasy is about. But if you’re going to write about war, and you just want to include all the cool battles and heroes killing a lot of orcs and things like that and you don’t portray [sexual violence], then there’s something fundamentally dishonest about that. Rape, unfortunately, is still a part of war today. It’s not a strong testament to the human race, but I don’t think we should pretend it doesn’t exist. I want to portray struggle. Drama comes out of conflict. If you portray a utopia, then you probably wrote a pretty boring book.”