Under what circumstances do division/dept directors feel compelled to attend temp staff interview together with DD and HR? The role is individual contributor, not even a junior team lead.

From my past experiences, usually directors don't bother with temp recruitment. Only at the DD level. Not sure if it's becos boomers and gen x can't be bothered with menial issues and leave DD decide who to hire, or millennial directors are more hands-on with recruitment and more micromanagey? Anyone who has worked with both gen x and millennial directors in recruitment care to share some insights?