I had an interesting conversation with a friend of mine who is big into Japanese history and fencing and mentioned this thread. One explanation he presented to why Japanese sharpened the swords so much and why such emphasis was made on attack is that Katana was basically a 1 shot kill weapon for every day (kinda like a not so concealed carry handgun for self defense). Many of Japanese schools concentrate mostly on draw and kill in 1 motion and Katana seems to be optimized for that. Being a cutting sword you can draw and hit faster then with a stabber (1 motion), being a cutter and extremely sharp not only will it kill but it will kill instantly, distinction is significant. You can be stabbed through the lungs or stomach and will die. but you just might take your opponent with you (old saying about knife fight with winner dieing in a hospital and loser at the scene). Blow with a katana inflicts such a massive wound that it disables opponent where he stands (think about stopping power arguments for guns), Katana is a stopper.
Another point he made is that what acceptable in term of fighting and duels is completely different in Europe and Japan. Look at how Musashi disposed of most of his foes, it was not from some extreme sword play but by surprising them. Once challenge is accepted if you can kill a person before he even draws he blade all the better. Even Japanese customs and rituals take it into account, when Samurai sat down he would place his swords in different location, some where he could draw instantly and some where he could not, that indicated the situation and status (if you are a lord your sword would be in the insta draw location, if you are vassal yours would not)
Another point he made is that what acceptable in term of fighting and duels is completely different in Europe and Japan. Look at how Musashi disposed of most of his foes, it was not from some extreme sword play but by surprising them. Once challenge is accepted if you can kill a person before he even draws he blade all the better. Even Japanese customs and rituals take it into account, when Samurai sat down he would place his swords in different location, some where he could draw instantly and some where he could not, that indicated the situation and status (if you are a lord your sword would be in the insta draw location, if you are vassal yours would not)