Why are so many guys like this?

I know this isn’t true of all guys but most of the ones I’ve gotten involved with are. This guy I went on several good dates with and who sent me a cute gif this week saying “you’re mine” just posted a picture of him and another girl right behind him in a dark room yesterday on Thanksgiving. I don’t think she’s family bc his immediate family lives far away so he didn’t get to go home. And he shares his location with me and he’d stayed the night. But then he texts me happy Thanksgiving and I just don’t understand how he could forget about me like this. Unless anyone thinks it’s just a misunderstanding.

Why are so many guys like this?
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