Why does my former friends with benefits insist on remaining friends?

Long Story, Short: We were FWBs for three months. I caught feelings, he did not reciprocate those feelings. I cut him off for my mental health and so that I can move on. Although, he is currently dating someone and despite the fact that we weren’t friends prior to this arrangement, he insists on staying friends.

I have blocked him on everything, but he has started emailing me. We he sees me within our mutual friend group (that I’ve taken a step back from specifically because I’m trying to avoid him) he hyper focuses on me and tries to get my attention. He keeps asking if we can talk.

What the fuck is going on? Do people usually continue to associate with former FWBs after it’s run its course.
Why does my former friends with benefits insist on remaining friends?
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