The main problem is there is no good way to provide manpages for shell builtins, like `command`.
Man can only have one entry (per section) for a given command, but what if you're using Bash? Or Zsh? How would it know which one to give you? If they're named differently (like a manpage for `bash-command` vs `zsh-command`), how would you know to look those up? (never mind that apropos would give you so-overloaded-to-be-useless results for something as generic as `command`)
Which leaves us in the current situation where `man command` redirects to a generic `builtin` manpage, that doesn't have much info, and certainly nothing specific to Bash or Zsh.
Man can only have one entry (per section) for a given command, but what if you're using Bash? Or Zsh? How would it know which one to give you? If they're named differently (like a manpage for `bash-command` vs `zsh-command`), how would you know to look those up? (never mind that apropos would give you so-overloaded-to-be-useless results for something as generic as `command`)
Which leaves us in the current situation where `man command` redirects to a generic `builtin` manpage, that doesn't have much info, and certainly nothing specific to Bash or Zsh.