How do you respond to the classic interview question of why do you want to do medicine?

I think it's important to be ready for this question but to ensure it's not a generic scripted answer. Even if this question is not directly asked other questions will definitely allude to it and the key is to link your answers back to why medicine is the career for you. The typical pros of the career include the vast amount of science you study and the direct application of these scientific principles on real people which in turn means dealing with the complexities of their lives. It shows you have true insight into the career if you structure these points within less typical points. For example you know you need to study a massive amount of science but if you say that the fact that as a doctor you never stop learning and that is something you are excited by, this shows you are conscious of the realities of the career. Also, I believe it's important to stress how rare and privileged a position being a doctor is as you deal with people at the most vulnerable moments of their life. Interviewers love to see humility in students!
In my opinion this question is thrown at students to try and gauge how much they want to do medicine by the way the answer is delievered. The people interviewing you know you're intellectually bright enough but want to see whether you have the drive and- I hate to use this word but- passion for the degree and thus the job. So it's pointless having a perfect answer with a perfect list of reasons unless you deliver it with conviction and are determined that you will prove to these people that you truly want to do medicine! I remember actually stumbling over my words a bit when trying to explain my answer as I was so engrossed in my reasoning. This isn't ideal but displaying your drive and personality is a good thing to do!