Working in the service industry is a means to an end for a lot of people. Even those who stay in the industry are working on accomplishing other goals, like finishing school or helping your family meet loose ends. The interviewer doesn't expect you to say you want to work at their restaurant forever, but they are interested in hearing your future plans. Wherever you're at in your career, let them know how this job will fit into your career goals. Here's an answer example: "I plan to work for your restaurant while I finish my degree, which I plan to complete two years from now." shows you are working towards a goal. Your role as a host will help you to achieve that goal by providing stability and income.
"I plan to work for your restaurant while I finish my degree, which I plan to complete two years from now."