I enjoy the tradition. In some cases it's informative--it helps me better understand the circumstances in which a technique arose, and hence to grasp it better--but mostly it just fits with the practice of martial-art-as-hobby for me. I like what I've learned about Japanese history and culture from karate, for example, but also like helping preserve a traditional art, as one might preserve a traditional form of dance, say.
Is it necessary? No, and in my opinion some tradition-emphasizing teachers should look to modern coaching methods in place of their traditional top-down. do-it-my-way style of teaching. I always like to learn the original way and the optimal way. The latter may well vary from student to student.
But yeah, the tradition, the legacy, the structure, the history, the culture, are all part of what keeps me in.