I think we like to systematize knowledge for two basic reasons.

1. so that we can learn more and remember more of what we learn.
2. so that we can feel better about the stuff we don't know.

As to the second: We seem to take comfort in the feeling that if something was important enough to be worth our time to learn, it would or could have already been systematized so that we could learn it. This notion itself is (somewhat comically) circular. In other words, implicit in the probability that something worth knowing would already be systematized is the notion that even systematizing is systematized. And it is. But some systems are more accepted than other systems.

And systems sometimes seem to be sort of like a project of assembling a multiple part puzzle. Often we work for a very long time, can tell we're nearing the end, and then we realize there's a piece or two left over that can't be made to fit externally, but rather might require starting over. But the project LOOKS complete (if we can find a way of destroying the evidence of incompleteness – the leftover piece(s)).

And in real life, when it's not just a puzzle, but rather, a real bit of evidence that just maybe the system under which we've assembled all our knowledge such as to hold it all conveniently usable has a weak spot or two, we may be under even greater pressure to hide, or hide from that evidence.

Maybe it's professional pressure. Maybe our employment is with a system manager (so to speak) and further investigation of weak spots may not just rock the boat, but throw us overboard.

Maybe its age with its alternating smugness and weariness. One day we're pretty content with our choice of system, and quite comforted by our surety that our system is better than their system (carefully making such comparative assessments while purposely avoiding the alternative systems that MIGHT challenge our smugness). And the next day, we're just too tired to even think about starting over with a new set of assumptions.

It's rarely about finding truth. It's mostly about comfort. And old folk want comfort most of all -- after all, they have the most to lose in the discovery that the bed they made isn't really up to the task of holding their weight for the long sleep.