Japanese culture places a lot of importance on taking care of yourself and not inconveniencing others. Sooner or later we all end up needing a little help, though, which is why the Japanese language has a half-dozen regularly used phrases that all mean “thank you.”
But while having that arsenal of expressions with which to show your gratitude comes in handy, it won’t do you much good if you want to thank someone who’s not in earshot, such as a fellow motorist who let you into their lane on the expressway. That’s why Japanese drivers follow a bit of automotive protocol that lets them deliver a message of thanks with the push of a button.