Today at work a woman with two girls ( one of them was 3 and the other 5) came in for a appointment,…

Today at work a woman with two girls ( one of them was 3 and the other 5) came in for a appointment, and the 3 year old cried from the moment she got into the waiting room until they left home (about an hour) I felt so bad for her, I know she was getting frustrated, she was walking around with her daughter, signing, holding her, she was trying everything to consult her and she didn't budge.

I don't understand why kids do this?