I think it's because most people prefer not to make a scene. They would rather avoid confrontation than confront someone directly. So, when someone goes to a restaurant and encounters a rude waiter, they can either leave quietly or endure the situation. It might depend on how hungry they are! However, those who don't complain at the moment tend to go online later and write a harsh review, which can be more damaging than addressing the issue in person.

Some people stay quiet about bad service because they think the company won’t bother to change. They feel like their complaint won’t make a difference. Also, they might doubt whether giving feedback actually does anything, so they decide it's not worth speaking up.

Some people don't speak up about bad service because they think it's just a waste of time. They believe that complaining won't change anything, so they don't bother. Also, they might not want to go through the effort of making a formal complaint, finding it easier to just let it go.