Whether in secondaries or interviews location can be a big factor. There's no reason to hide it. Let's say it's because family is nearby:
Interviewer: "So why choose MYSTERYCOM?"
You: "Well, at first it was simply because of location. You are by far the closest school to my family an an obvious choice for me. Yet, when I began looking into things I realized that your reputation, faculty, facilities and students were all superb. I feel comfortable in this place, and I've always believed that I excel when I'm most comfortable. I'm sure that I would be happy at MYSTERYCOM if it were located a thousand miles away. It's just a bonus for me that you are so close to home, don't you think?"
Make sure you look the interviewer in the eye and nod affirmatively at this point. If he nods back, you've taken control of the interview and you are in for sure 🙂
One of my top criteria was to go some place warm. Quite simply, I'm miserable in cold weather. I just hate it. So.... my choices were somewhat limited. I said pretty much the same thing as above in interviews and substituted how comfortable I was in warm weather instead of having family close by. It lead into a rather humerous story about the last time I was in ice and snow. Honestly, it really doesn't matter what you say in an interview.... it's more of how you say it. The same goes with secondaries. If you make what you are writing or saying interesting, then the subject is a moot point.