They could be yelling because they are in a competition or trying to get someone's attention. Sometimes, it's just a way for them to express their emotions freely.
Zuko's complexity makes him so interesting in these fanfictions. He has a troubled past which has shaped him, but he is constantly evolving. His ability to show vulnerability in front of the reader is another great trait. It allows for a deeper emotional connection between him and the reader, as seen in stories where he opens up about his insecurities and fears.
The bellhop could have been yelling because he was caught up in the intense and confusing situation, trying to make sense of it or get someone's attention.
Perhaps the old man yelling in the cartoon is a symbol of protest or a way to express dissatisfaction. It might have a deeper message or just be for comedic effect.
Women yelling in cartoons might be used to emphasize a character's emotion or to drive the plot forward. Maybe it's to show their frustration or to catch the viewer's attention.