It's largely because they're dealing with an area with no theoretical tools. Any time you hit an area that are full of people "Designing" solutions/abstractions rather then "Calculating" an optimal solution/abstraction you know you've hit an area where there's very little theoretical knowledge and most people are just sort of wandering chaotically in circles trying to find an "optimal" solution/abstraction without even a formal definition of what "optimal" is.... I mean what is the exact definition of the "perfect abstraction"? What is bad about duplication what is a bad over abstraction and what is this "cheaper" cost that the title is talking about? It's all a bunch of words with fuzzy meanings injected with peoples biased opinions.
That being said theories on abstractions do exist. If you learn it you'll be at the top of your game; but it's really really hard to master. If you do master it, you'll be part of a select group of unrecognized elites in a world of programmers that largely turn to "design" while eschewing theory.
Here are two resources to get you started:
The Algebra of Programming: https://themattchan.com/docs/algprog.pdf
Program Design by Calculation: http://www4.di.uminho.pt/~jno/ps/pdbc.pdf
You will note that both of these resources talk about functional programming at its core which should indicate to you that the path to the most optimal abstraction lies with the functional style.