My Norwegian is terrible at best, Swedish while similar is not the same and it adds a level of complexity to things. Rather than my learning "back carry throw" in the language of every place I visit, I can just learn "seoi nage". I have played judo with people from five continents. Rather than all of us learning every single language, we have learned the lingua franca of the sport.
If you have no desire to travel, compete or have foreign players visit then there is no need to learn Japanese, but for those of us who do, it is a tremendous help.