Why does my married coworker keep joking with me instead of talking normally?

I’m quite a serious and sensitive person not sure if it got anything to do with it but everyday he has to say something jokingly why can’t he just speak to me properly the fact that he is a very professional person at work I don’t understand sometimes

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3 h
He already knows I’m sensitive
Why does my married coworker keep joking with me instead of talking normally?
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