Why do the Japanese not give reasons when they apologise, refuse invitations and deal with complaints?

Countries tend to fall into two groups – ones like Britain and America where not giving excuses is seen as not being bothered to do so or being deliberately rude (like saying “I’m busy” to an unwanted date invitation), and ones like Japan where giving excuses is seen as not accepting responsibility (like saying “The dog ate my homework”).

Just added to my much expanded Japanese Etiquette and Manners Explained page.