I've noticed that too, especially during sales or in December because of the holidays. It's so annoying.
The other day, the woman in front of me mentions nicely to another woman that she's jumping in and she gets mad. Excuse me but she's the one who's jumping in, so why does she get mad? Then, the saleswoman told her nicely to get in line and that woman got mad again, said that she would never come into that store again and left.
Some people can be so rude. Besides, I was the last one in the queue and there were only 3 women in front of me. She wouldn't have had to wait for a long time, maybe 5 or 10 minutes.