I hope that get remind of their dream boy and kiss other guys considering them as their dream boy, which he actually isn't.
Girls just want to enjoy the time fullest, They can't control herself to be lost in passion..... or a girl explain it more better....
It's rude to stare! When you close your eyes it feels like you can cut out every other distraction going on around you and increases the intensity of the kiss making it more passionate. Men and women do this by the way. I don't know why you keep your eyes open...
I think you are an experienced person about it ? I think the kissing persons in your image file are Shahid & Kareena.