You're confusing computer science with writing software to run on hardware. Coding requires the latter, but not the former.

Oof, and to think one could helpfully inform the other! :) To be clear, I am a programmer, not a computer scientist, so my opinions are based off writing code and managing teams to write code that works, and less so about abstract machinations of computer scientific thinking.

For the record, I generally think that people exaggerate the complexity of Functional styles.

I think the reason that stateful, imperative code is the default is because that is how we tend to "think". Example, if I wanted to get a list of items for the grocery store, I get a piece of paper (instantiate an array), go through the list of things I might need (loop through a source array) and write down the ones I definitely need (append onto the destination array). If I run out of space, I get a new piece of paper and continue the process.

With that algorithm, I can stop and test each individual statement; I don't need to "think about it" because I can write and execute a tiny part of it (even if I'm only executing it in my mind).

In a functional style, I have to think more declaratively. Given all my items, filter out the ones that need replacing and give me that list. It's much easier to reason about abstractly, but I have no details about w how that's actually happening.

I think this kind of thinking is superior most of the time: I would rather read map.filter.reduce more than a for loop with branch statements any day of the week, but I am trusting the implementations of the mapping and filtering and reducing functions. Of course, for any non-trivial algorithm one is still passing a function into the map/filter/reduce anyway so I can still reason about those smaller stateful sections without worrying about the map/filter/reduce piping.

Perhaps I've never worked in a truly pure functional style so I may not be dealing with the mountains of abstractions others seem to complain about