If you have plenty of potential job leads and you find yourself in the position of sifting through them for the best one, that may be true. That's not the case for most people.
I would go one step further: why would the question be irrelevant for a janitor? Let's say you search for a janitor for a high school. You have three good candidates. One just applied randomly. One lives just around the corner, and wanted to find a workplace where he would not have to drive for hours. The third one lives far away but loves interacting with teenagers: for instance, he is a karate instructor in his spare time.
Feels relevant to me. You can apply for a janitor job in a lot of places, so it cannot hurt to ask whether there is a reason to choose this particular one. As other said, just saying "I need a job and this fits my profile" should be an acceptable option.
Let's not pretend that question is what will make or break the interview. I always see it more as an ice breaker to get the discussion started.