Why do some parents laugh when there kids misbehave?

I work as a cashier and today there was a little girl who threw a fit (screaming and crying) because her father wouldn't buy her some things she wanted. She screamed so loud that I couldn't hear what another customer was trying to ask me. Instead of making her stop or taking her out of the store her father just laughed. Would any of you who have kids of your own have laughed in the same situation? The girl was between 4 and 8 years old.