Because complexity isn’t formally defined. We don’t have any formal definitions of what it is and as a result we don’t even have any algorithms that can reduce complexity.

Thus because there is no theory, much of software is like art. Just a bunch of arbitrary techniques. That is what OOP is. OOP techniques have no basis in theory or formality yet it masquerades as something formal with big overly complex nomenclature like dependency injection and inversion of control as if any of these techniques mean anything formal.

I digress. Anyway because we don’t have a formal definition of what complexity is we often dont know what direction we are moving in. Is it more complex or less complex? Who knows?

So until someone comes up with a formal definition of what it is we will just be moving in circles.