You guys can do it and then forget about it, it doesn't make any different. But it is different for a girl. A girl has to protect herself, because there are things that cannot be regained once lost. We have to protect ourselves till we find the right person to share it, or else what would be left for a girl to share with that special person if we go for it before that right moment.
There is a time for love, there is a time for sex, and waiting for the right moment is a wise decision. And a rash decision can make the whole life different.
I don't know how it is for you guys, but men and woman cannot be compared in this context. Scientists and researchers say that men are more sexually active than woman. But it is not that we don't want it, it is that we "can wait" till it is the right time for it.
It is not that we are afraid to talk about it, but a girl wouldn't talk about that with a total stranger. If she is very close to you, and in a committed relationship with you; you should find a good peaceful moment and bring the topic and discuss, because we are generally shy to start the topic.
There is one thing for sure, I believe that girls are more concerned about our sexual health than you guys.