|I am trying to better understand what some of the languages mentioned here do. After a cursory look, I'm unsure why each one of them was written.|
Why did you write these programming languages? Are you personally using them? Have you written say your website in them, or some important tool in them?
| Arc/Nu seems like a cleaned-up Arc, and faster.
| Anarki seems like it improve Arc with the non-compatible changes.
| Arcuid seems like a backwards compatible Arc, but transformed in C.
| Wart seems like a Python with macros and more flexible syntax.
| Subjective Lisp puts Arc in iOS
Of course there's fun and educational value in writing a programming language. You get to discover esoteric features you wouldn't have known otherwise and dig deeper. There's also unchartered territory beyond just a language. When one writes a new tool it's usually (hopefully) to satisfy a pretty frustrating need.
Can you point to the exact utter breakdown of some existing language that had you throwing your computer out the window, refusing to touch one again unless there were a language that could instead do X?