1) Writing frameworks in languages like C++ is hard. So you would expect to see fewer frameworks.
2) When a language is popular, like JavaScript, you get a lot of activity. (Notice the lack of new COBOL frameworks on Hacker News).
3) JavaScript can be fixed with polyfills, frameworks, monkey-patching, etc. So we fix the language until that fix is part of the language.
4) JavaScript is almost perfect for writing web clients and servers, and we're all trying to fix that 'almost' part.
5) Ego is part of it - you have to engage in some level of promotion (otherwise you can't cut through the noise).
6) It's fun. It amazes me what I can do with JavaScript some times. I wouldn't mind doing that all day.