I like this question as an interviewer.
It lets me know how much the prospect has thought about the position or if they are just going through the motions.
If we listed every thing that we do in the job advertisement, it would essentially be unreadable. Also, cultures vary from institution to institution, so it helps us answer those types of questions.
I always have different genres of questions prepped before I come in because you know they are asking this. My problem is I always tend to weave them into the interview, so don't have much left at the end. However my interviews tend to go long as it turns into a real conversation where we are both feeling each other out, so its ok. Also doing this makes them skip the bs questions like "where do you see youself in 5 years" because you are so job skill and opportunity focused.
I got turned down for my first real job ever recently, only based on the fact I had applied before, was offered, but declined as I had 2 other offers that week as well and one was substantially better (financial only turns out, not fulfilling). They wouldn't even email me telling me they knowy skills and want to go in a "different direction". I loled.