In the modern of here and now, what place to historical training tools like the Japanese sword (katana) have?
If one is studying the martial arts for modern applications why study kenjutsu?
Could one debate that in order to truly understand the Japanese martial arts, one must study kenjutsu- Japanese sword use?
The Japanese martial arts of today are based on the skills of the samurai and their historical martial arts. Judo, jujutsu, etc. have their roots in the samurai.
For the samurai the use of the sword and other battlefield weapons such as the spear (yari) was central. Naturally much of their philosophy, strategy, and tactics was build on these weapons. Many of the advanced forms studied in the martial arts are communicated through the lessons of the sword.
There are also spiritual benefits that can easily transfer over to modern applications- so much martial wealth and culture is locked in the sword.
On a practical level, as a training tool the sword is easy to understand and challenging to use- many lessons about distance and timing can be seen using it, and if one can see those lessons and understand those lessons, those are further life skills that transfer over to the here and now lessons of today.