What's the point of jealousy (I find it stupid and toxic) in a relationship?

For instance I got dumped because he wanted to see other people.

My reply as I'm opening the door (my house): The door is open. Don't stay there for too long though. Otherwise you would be blocking the traffic.''

He was shocked that there was no jealousy tone in me, at how I can be calm. He kept bringing back the stereotype that we (you probably know which ethnicity I'm referring to and no not all of us are like that) can be feisty, jealous, somewhat crazy and very loud. My reply: ''Ok bye, the door is open now. Like stated, you're blocking the traffic right now''. Then he left.

I'm still wondering what's the point of being jealous and crazy? I find that a terrible trait.

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Why would I try to chase someone that doesn't want me? It makes no sense. Or those that keep saying ''that man/woman stole him/her from me''. Nope, no one stole anyone. They want on their own because they wanted to.
What's the point of jealousy (I find it stupid and toxic) in a relationship?
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