A quick wikipedia search would tell you all you need to know about the role of the knife as a keeper of honor and, sadly, a quick draw weapon for wounded pride. A Samurai would keep a short sword or dagger on hand at all times to preserve their honor, whether against a foe in a confined space, or on themselves if need be. The Romans also kept a pugio at hand as a status symbol, as well as to defend or perform assassinations. (et tu, Brutus?)
Even in more modern times, knives are often the go-to weapon for juveniles looking to prove their worth. Think on Rebel Without a Cause. A classic fencing scene, though whereas the rapier was the weapon of a thug before the nobility took it up, the same distinction befell the switch blade. Even today, knives and daggers, though not widely carried by the public at large, are still used to settle matters of "honor" between less reputable sorts. Though most prefer guns. <_<
The knife has a long and sordid history, yet for those who lead an active lifestyle, there is no tool more versatile than a sturdy blade with a keen edge.