Why would someone who rejected be so determined to be friends with you?

This guy rejected me but he insists on being friends despite the fact that I’ve made it very clear that I don’t want to be friends.

What gives? I’ve never had this issue. Usually when I’m rejected (“I don’t want a relationship”), they typically leave me alone and don’t care whether or not we stay friends.
Why would someone who rejected be so determined to be friends with you?
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