Why would a guy ask why you like him?

He always knew I had a crush on him (for a few years). He asks, "I want to ask, after a few years why you still like me? What's something I have that makes me different from the rest?" It almost sounds like he couldn't believe someone like me would like a person like him. What reasons could there be behind asking someone "why" you like them? Is it genuine curiosity?
Why would a guy ask why you like him?
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