One benefit is that it makes the animals happy. Happy animals are more likely to be friendly towards us. For example, a well - treated dog will wag its tail and be excited to see you.
Being nice to friends can lead to more enjoyable social experiences. If you are kind and positive in your interactions, your time together will be more fun. Also, it can expand your social circle. When your friends see how nice you are, they are more likely to introduce you to their other friends. Moreover, being nice to friends helps in reducing stress. A harmonious friendship where everyone is nice to each other is a source of comfort and relaxation, rather than a source of worry or conflict.
One idea could be that Bakugou wakes up with a strange quirk malfunction that makes him overly nice. He starts complimenting his classmates, which leaves everyone in shock. For example, he tells Deku that his analysis skills are actually really impressive. This throws the whole class dynamic off, but in a really interesting way.
One possible analysis could be that their relationship in fanfic often showcases a strong bond of friendship. Bakugo's explosive personality and Kirishima's more stable and friendly nature create an interesting dynamic. Fanfic writers may explore how they support each other during battles or in their daily lives at school. For example, Kirishima might be the one to calm Bakugo down when he gets too riled up, and Bakugo could inspire Kirishima to be more confident in his abilities.
Bakugo is known to curse in the manga. This is used to emphasize his strong emotions and aggressive nature. However, the frequency and severity of the cursing might vary depending on the context of the scene.