Rank is in the eye of the beholder. What does my rank mean to me? That I'm closer to doing what I'm doing now in a hakama and black belt than I was at my previous grade. Hopefully I'll be doing it better but I don't see how changing my uniform or gaining a higher rank affects my daily training and therefore I see no point in it.
What does it mean to other people? Depends on the person. To my instructor it defines how picky and grumpy he should be when I do a technique
It doesn't mean much to the other people in my dojo, no-one can remember what rank I am, including my instructor.
What does it mean to anyone else? Probably nothing. To the uneducated eye I'm a total beginner because I wear a white belt, to the uneducated in general the term "2nd kyu" is totally meaningless. Women certainly aren't impressed
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To other Aikidoka it means that at best I tenkan without falling over, know which end of the bokken to hold and can occasionally do something right
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Why do I grade? Well I'm at HQ dojo during the gradings anyway so I may as well get up and grade. That may change when they ask me to take dan grade and pay up £500 to attend summer school for a week, get graded and have Doshu sign a certificate for me, all so I can get back to training the week after in a skirt and a black belt.