There is a good chance the candidate doesn't aspire to work specifically for you, rather you were one of the company’s they applied to in their search.

When you ask this question you are asking for a socially desirable answer or, in other words, you are waiting for the candidate to tell you what you want to hear. All you will learn from this question is if the candidate researched your company in advance — nothing about their motivation.

If you want to understand a candidate’s motivation you can ask questions like:

What other positions have you applied to?
Which components of your current or previous job did you like and dislike?
What are the job’s key components you are attracted to? which ones are you concerned about?
If you had a chance to earn more and do less of (liked job component) or earn less but do more of (liked job component) - what would you choose?

Image Source: Bored Panda