I don't get the logic behind the sharpening pyramid? Why go from a higher grit to a lower grit?

When you do that aren't you just negating all the work done with the higher grit?

I understand going back to a lower grit if you decide that you left it prematurely (through trial and error) but to plan on going back and forth...what is the logic behind that?

(Edit) Sorry I just noticed that there is a "Honing" section as opposed to this section on "Hones".