The reason a giraffe has a long neck is quite simple. It's for reaching leaves and branches that are out of the reach of shorter animals. This adaptation gives them a competitive advantage when it comes to finding food.
Well, in Pulp Fiction, the bandage on the back of the neck is part of the movie's unique aesthetic. Tarantino often uses such details to create a distinct look for his characters. It could also be related to the non - linear narrative. Maybe in a part of the story that we don't see fully, the character gets injured there, and the bandage is a constant reminder of that unseen event, adding to the enigma of the character and the overall story.
It makes the character look a bit more rugged. The bandage gives the impression that he has been through some rough stuff, like a street fight or an accident. It's like a badge of a recent misadventure that adds an edge to his look.
The giraffe has a long neck mainly for reaching food sources. It's an adaptation that developed over many generations. Those giraffes with longer necks were more likely to get enough food and pass on their genes. So, gradually, the population ended up with mostly long-necked giraffes.
In the light novel, Dazai's fate is not a happy one. His death is a crucial element that shapes the overall tone of the story. It's not a storybook happy ending where he rides off into the sunset. His end is more bittersweet, if you will. It affects the other characters deeply, and the story moves forward with a sense of loss due to his death.