It's odd that they are all technology or language specific (except for API - which covers REST).
I don't think this is accidental. Industry knowledge is becoming fractured across technology and tools. People rarely consider that there are design guidelines that work across all software. I don't know why.
People need concrete context to get the knowledge? Most of us start with doing other than having the big picture? Most of tutors need to provide some taste in real world to learners to make them pay since programming is actually very practical? My guess is that these could be among the ones of the main reasons. Well, there are of course some motivations from educators' side as well. Maybe too simple and straightforward is not a good thing. I'm not sure yet.
I don't think this is accidental. Industry knowledge is becoming fractured across technology and tools. People rarely consider that there are design guidelines that work across all software. I don't know why.