This question already has an answer here:
Its a common question and of course very natural for an employer to ask an applicant: "So, you have a job at the moment, then why do you want to change?"
I guess the best I can do is to give a genuine answer: "Want to see a new company, fits better my interests, closer to my living place, see more perspectives, ...".
Or would this be too much about myself, what's the benefit for the company when I work closer to my living place? So would they be happier when hearing
"I think in this position I can deliver more value to the company" or something like that?