I was amazed that viewfinder of my camera has a 4 x 4 grid. Why is this? There's no 3 x 3 grid. Sad. What is the reason to did it so? Is it possible to fix it (upgrade software of camera)? What cameras do have 3 x 3 or golden ratio grid?
See this on the golden ratio and this on the rule of thirds. In short, these "rules" aren't very well supported as rules, and Nikon's assumption might be that they're unlikely to be very important to someone buying a mid-level DSLR. The even division has the advantage of showing you the center nicely, and simply having more lines is nice for alignment because it's more likely that something linear in the scene will correspond.
You can't change this in software, as the lines are physically on the screen. I don't believe Nikon makes official replacement, but you can get third-party focusing screens from KatzEye Optics with various grids, including "Rule of Thirds Grid" and various crop lines for 8×10 or square format or etc. If you really would like golden ratio grids, they'll do that too as a custom option.
Alternately, it looks like the corner focusing point indicators are on or very close to thirds; you can use that for composition instead.
I'll argue that it's about perception: I don't see a 4x4 grid when I look through the viewfinder, I see three horizontal lines and three vertical lines. Where the lines intersect create the "rule of thirds" guidelines.