…is what people in Japan say when their kids are writing kanji.
Why? Because of the translations available for polite, one (丁寧 teinei, an adjectival noun) would be more correctly translated as “careful” and the other (礼儀正しい reigitadashii) as “with correct etiquette”. You hear the former a lot if you work with kids, but seldomly with reference to disrespectfulness – it usually means something more like “slow down and take your time to do it right”. The latter word is considered a good thing but not an admonishment for kids or a general character trait.
This distinction is a bit beside the point, because when people in Japan describe their own ethnic group and society (these are considered the same), the words they use are やさしい yasashii or 親切 shinsetsu “kind/nice”, not any form of polite.
It may surprise American readers to hear that Japanese folks generally see their countrymen as sentimental and deeply emotional, not dry and detached “worker bees” as the stereotype goes. This is an interesting contradiction, because “polite” (but insincere) is probably the first thing Americans think of when they think of Japan. In Japan however the standoffish and deferential behavior that Americans consider “polite” when they come here is generally thought to be an expression of kindness and sincerity.
There are a host of public behaviors that are thought to show kindness in Japan, but the One to Rule Them All is 人に迷惑をかけない hito ni meiwaku wo kakenai “don’t bother people” (literally “don’t attach disturbance to people”). The default posture for a decent and kind human being is to assume you are the least important person in any room, and to apologize for any attention you attract, good or bad. Because you are as a matter of general principle unworthy of people’s attention, presuming that whatever you want from them is worth distracting them from what they’re already doing is a huge trespass, whether you want to ask where the bathroom is or want them to stop throwing rocks at your head. One result of this is that some common forms of thanks are すみません sumimasen or 申し訳ない moushiwakenai, which your dictionary probably translates as “excuse me” and “I have no excuse/I am deepy sorry”. Even if the other person did a favor for you clearly of his/her own volition, you are supposed to apologize for making them think about you. This reluctance to disturb anyone else for any reason can produce situations that look like people are being “polite” to each other.
People see this concern for others’ time as kindness, not as politeness, because it supposedly comes from empathetic regard for and elevation of others rather than respect for them as equals to oneself. In fact others are clearly not equal – you’re inferior to them. If it were polite in the American sense, it would come with self-respect as well, which is one thing that is conspicuously absent from formal interactions in Japan. Dave Barry captures the mutual vacuum of apparent self-esteem that often results:
First businessman: Hello, sir.
Second businessman: Hello, sir.
First businessman: I am sorry.
Second businessman: I am extremely sorry.
First businessman: I cannot stand myself.
Second businessman: I am swamp scum.
First businessman: I am toenail dirt.
Second businessman: I should be put to death.
The principle of not bothering others has gained self-awareness in Japan, where it has been elevated in the collective consciousness from the particular Japanese expression of a common human trait to a uniquely Japanese trait, along with omotenashi and mottainai. I can’t comment on the commonness of this kind of thinking in most countries around the world, but it’s definitely alien to most people from the US, where the right to crush anyone that gets in the way of your self-actualization is in Article 2 of the Constitution.
One final note: I keep referring to “Americans” not “Westerners” because “Western” too often simply means “white”, and also I have no clue how Germans or Portuguese folks behave in public. I shouldn’t even generalize about Americans as much as I do, but I hope readers will know to take generalizations about the US with a super-sized grain of salt.