Q:

Why can I close my question as too broad or unclear?

Why is there an option for me to flag my question as too broad or unclear what you're (I'm ?!) asking?
I don't think anybody will use these flags for its own question! Flag as duplicate seems right, but other flags are not so useful for own posts.

A:

For the same reason the Disciplined badge exists: for users who are self-aware and humble enough to acknowledge that their question isn't a good fit for the site or isn't clear after all, and for whatever reason choose not to edit their question — maybe they think a rewrite would take so long it's best to get it closed first to prevent answers, or they'd just rather get rid of it and forget about it than try to re-scope it or clarify it. (They could also just straight-up delete their question, but they won't be able to if there are already upvoted answers, which leaves closing as the next best recourse.)

