Its been covered on here before that some people don't care about earning rank in the martial arts, if they train in a style that uses a ranking system, and I know that rank isn't everything but here is a reason why it might be important in some situations. Sometimes when you're discussing martial arts with somebody they might ask you at some point what your rank is, where you got it, ect. and if you're not at a high enough rank they might not take you seriously. Now when I talk about a "high enough rank" that's very subjective of course but I would say that if you've at least made first dan in a style you're going to be taken more seriously than if you haven't. Also, it would depend on where you earned your first dan rank and the standards you had to meet to get it. There are some schools where I wouldn't take a person seriously even if they got third or fourth dan there because they've got such low standards, but if its a good school with a good solid reputation than I would take a person who earned first dan there as I believe most in the martial arts community would. So that is just one reason why rank might be important to some people.