Why is it important to you to rank up, anyway? Your signature doesn't look like it's advertising, so are you looking to get into a campaign or something?
Probably but the main thing I can think of is avatar. I recalled I have different feeling when I can wear an avatar.
Another time I got good feeling when I ranked up from Full member to Senior Member and can wear a signature code with different effect. From Sr. member to Hero and Legendary member, I don't have such feeling because signature display is almost the same.