Why are most girls and women mostly upfront about their feelings?

My girlfriend isn't afraid to show her feelings. When she gets emotional, she shows it. When something upsets her so much that makes her cry, she shows it and isn't afraid to do so. Her mom is the same way. Don't get me wrong I admire her for that. I hate showing that I'm crying. Men don't cry. Ladies how are you so straightforward about your feelings?