well that's a sweeping judgement!Any woman who is shy about liking it rough just isn't comfortable with her sexuality. I like it rough at times, some of my best orgasms occur during rough sex and it isn't anything to be ashamed of.
maybe she just isn't sure enough of her partner.
i'm open about it when it comes to sex, but that's because i wait months (often years) before i'll sleep with a guy. i know them well enough to know that they won't be freaked out, upset, intimidated or tempted to take advantage.