How come Women get mad or upset when this happens?

Okay pardon my ignorance ladies,but i watched a movie called The Wackness.And it showed a scene and the guy was the virgin,and the girl sits all of a sudden and she's like *did you seriously,just...* and then she got mad and got off him.It wasn't till i did some research i found out what happened.I've never had so i don't get it,how come women get so upset if a guy....*comes* too soon?