Everyone likes to think of battoujutsu as a God-given gift, and that only few people can manage it. However, battoujutsu is as real an art as painting and singing, and had been practiced centuries ago by people yearning to protect themselves.
Japan is a forward-looking culture, and knew things more than we give them credit for. Battoujutsu had been created as a way for samurai to protect themselves while walking on the street in the cities of Edo and Kyoto. Nobody wants to mess with somebody in armor, but someone in civilian clothes can be a target for assassins and thieves alike. It is generally impossible to be able to draw your sword and assume a stance especially when there are lot of undesirables coming at you. Hence, the need to be able to draw and attack at the same time.
Of course, Kenshin Himura and his god-like speed are products of fiction. No one can move that fast, not even the best of swordsmen. They just look fast because the eyes of their enemies cannot keep up with them, as well as the eyes of spectators. Only practitioners who have the same level of skill as they do can be able to keep up but they're bound to be unable to keep up every now and then.