Analogy is in programming itself - divide up a program into modules that each have a very clearly defined interface. Then people can work in parallel on it. I know everybody agrees with this, and it is stupidly obvious. But time after time, I see source file after source file importing (or #include'ing) every other module in the project. A pull request to fix a problem affects 10 files instead of one.

It seems to me that people are simply terrible at modularizing code. (Including me.) I've seen this problem far more often than not, in every organization I've worked with, for my entire career.

Just the other day I worked on a function that did some Windows API calls for file I/O, allocated a bunch of memory, and processed the file contents. I split it up so the code that needed the Windows API did just that - it didn't allocate any memory, and the processing was done with a callback.

That meant the Windows API accessing code didn't need to import anything from the rest of the program, and the rest didn't need to import the Windows API.

(There are some success stories. The popularization of generic algorithms and ranges (or iterators) has been a big improvement. And the use of global variables has become frowned upon.)