One reason not to pick up hitchhikers is that you never know who they really are. They could be criminals on the run. For example, in many horror stories, a hitchhiker turns out to be a serial killer. Once in the car, they can pull out a weapon and put the driver's life in danger. It's just too risky to stop and pick them up.
The 'Don't Pick Up the Soap' manga could be significant for its unique art style, complex characters, or the way it challenges conventional storytelling. It might also offer insights into uncommon or overlooked aspects of life.
Sometimes in a story, not picking up the phone creates suspense. Maybe it's a call from someone the character is avoiding, or it could disrupt an important moment or plan they have.
Well, it's claimed to be based on a true story. But like many such claims, some creative liberties might have been taken to make it more engaging for the audience.