Why doesn't JSON allow trailing commas? Why? How hard is that to implement? Everyone else has them, why not JSON?

Javascript: trailing commas are OK.
JSON: trailing commas are Unexpected token '}' in JSON at ...

Dear Python linters, why can't any of you implement some actual linting features? Like, say, consistent use of single or double quotes? Or dict() vs {}? How about indenting nested function calls? Forcing list / set / dict literals as multiline? Trailing commas?

And while I'm at it, why can't you handle dependencies properly? Say, separating linter & linter plugins from the remaining dependencies in a way where I don't have to manually remove them from the requirements lockfile every time?