Mathematics is supposed to be a foundation to model the real world. Basically i represents a situation where the square of a quantity results in a sink as opposed to a source. For example, the volume of water that goes down the drain that is a square pipe is (i times w (width of one side of the square pipe)) squared.
In 2 d space, whenever you see i, that means it is a sink, not a source and this is important in chaos theory too. As far as we know, nullity does not exist. Zero does not exist. There is no situation where all quantum numbers are zero. The essense of quantum mechanics is that there is a graininess to the universe or there is in fact an indivisible quantity. Even empty space has an indivisible quantity or is discontinuous.
Zero is a decent approximation to things that are "normal" to humans. But division by zero makes no sense to a "normal" situation and in the abnormal (incredibly small), zero does not seem to exist.
Nullity has little or no use in mathematical modeling while i has a great many uses.
As far as we know, all numbers are imaginary. some just hurt your brain more than others.
The mathematicians I have known aren't looking to model the real world with their math. They are trying to make intellectual discoveries and leaps in math. And if they eventually lead to something that models the real world, great. But it's not their raison d'etre.