This is an important question to ask in an interview because if you are offered the job, you will have to work in the environment affected and shaped by your predecessor.
Perhaps this opening was recently created to support company growth. If that is the case, ask a follow-up question about who owned the responsibilities up to this point, and how the duties will be transitioned.
If you are interviewing for a position left vacant by someone’s departure, get a sense for what happened. Why did the predecessor leave the job? Was he or she promoted or internally transferred? If the predecessor left the company, ask about the circumstances.