By asking this question, the recruiter wants to know how passionate you are about the role since this could be a strong indicator of your commitment and future performance. Your answer should reflect a deep understanding of your role.
"Receptionists are the front line of the office so it's very important they do their best in representing the business. A receptionist's appearance, manners, knowledge and helpfulness reflect on the entire company. The ability to communicate clearly and address issues in an organized manner is what makes a receptionist an ace at his/her job."