I really cant see any situation where knowing swordfighting is useful. Obviously doing it will improve your physical shape and balance and such but you can get that by practicing other skills that are actually useful outside of the sport
Hey, it can still be used as self-defence!
Sure, if you carry a sword with you at all times
While it's true that most people wouldn't have swords readily accessible during a self defense situation, it's not outside the realm of possibility for someone to have access to a stick of some sort. A broom or mop handle, a walking stick, or any other relatively swordesque item can be used with great effect by someone who is trained with the sword.
Also, a lot of sword training systems teach hand to hand techniques as well. Lots of disarming techniques, throws, and joint locks... Maybe not as intensely developed as something like aikijitsu or jujitsu, but still included in most curriculums.