You know what grinds my gears? Pages upon pages of 'useless'[1] anime guest-characters, and yet when I tried to add pages for real-life artistes from my (3rd world) country, I had the pages deleted for "lack of notability". This must have happened a decade ago, but I told myself "never again". Now I ignore Wikipedia's pleas for content under their "Wikipedia loves X" campaigns because I know they don't mean it. I doubt Wikipedia's cultural bias can ever be cured with the current editorial structures.
1. Useless to me! This is very much tongue-in-cheek
Sadly, wikipedia doesn't support the notion of citing "art installed at so and so location, viewed by so and so people" unless someone wrote it down in a western publication.
In a real sense, an encyclopedia is a history of books, not a history of the world. This is an unfortunate consequence of writing's special "viral" place among forms of communication, and the medium is the message etc
This is emphatically not the case in my experience. I believe I wrote a runge-kutta numeric solver using the wikipedia articles as the source. It was sufficient for my purposes. And yes, Wikipedia is not a textbook. You might want to be more specific what "improvements" were attempted. If you mean something like exercises and lengthy, worked out examples, then that's right, I'm not sure that fits in wikipedia more than it fits in a book.
I do not have time to write a well written concise article, so I have just copypastaed some stuff I don't understand.