Ask HN: Why don't we mention availability/timing expectations in job posts?

To get a clear indication of work-life balance in a role, for both kinds of posts - who is hiring, or who is seeking.

Working hours, on call/support expectations, frequency/duration, compensation for extra hours etc.

In fact the companies (startup or otherwise) posting requirements, at least here on HN, ought to definitely mention such requirements if any, and absence of it if there's none.

Why don't we put it all out there upfront?

Or is this not important enough? Or is it globally frowned upon if a candidate wants to discuss that?