Then in addition to that, we attach "meaning" and "purpose" to our defined qualities. These are abstract qualities that cannot be observed directly unless measured by some quantitative scale (which is ironically defined by qualitative observations). For example, superiority. To measure superior intelligence, you have to take an IQ test. To measure superior building ability, you may ask how many years experience an individual has building. We can only really observe superiority as compared to inferiority which is of course defined as the absence of superior quality. As you can see, all these abstract qualties give rise to dichotomies where the absence of one defines the other. Black and white, cold and hot, wet and dry.
The final step is that we associate "meanings" and "purpose" between abstract concepts in a sort of web fashion. Think of all the terms that mean the same as black. Dark, hopeless, dirty, angry, evil.
black - Synonyms from Thesaurus.com
This last step is where we get in trouble because we are associating abstract qualities with things that can't be observed or even measured.
So you asked why we "compartmentalize", "categorize", and web things together. That is because that is how the human psyche is developed from birth and probably even beforehand. It's how we learn to interpret experience.
There are alternative ways of course. The Taoist developed a paradoxical and unifying view of the universe that I find fascinating. For example, understand that black and white are defined as different and opposites, but also realize that they are the same thing, light.
I don't know if that helps any.